Merge remote-tracking branch 'origin/tracking' into custom

dom/base/UseCounter.h

@@ -0,0 +1,36 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef UseCounter_h_
+#define UseCounter_h_
+
+#include <stdint.h>
+
+namespace mozilla {
+
+enum UseCounter : int16_t {
+  eUseCounter_UNKNOWN = -1,
+#define USE_COUNTER_DOM_METHOD(interface_, name_) \
+    eUseCounter_##interface_##_##name_,
+#define USE_COUNTER_DOM_ATTRIBUTE(interface_, name_) \
+    eUseCounter_##interface_##_##name_##_getter, \
+    eUseCounter_##interface_##_##name_##_setter,
+#define USE_COUNTER_CSS_PROPERTY(name_, id_) \
+    eUseCounter_property_##id_,
+#include "mozilla/dom/UseCounterList.h"
+#undef USE_COUNTER_DOM_METHOD
+#undef USE_COUNTER_DOM_ATTRIBUTE
+#undef USE_COUNTER_CSS_PROPERTY
+
+#define DEPRECATED_OPERATION(op_) \
+  eUseCounter_##op_,
+#include "nsDeprecatedOperationList.h"
+#undef DEPRECATED_OPERATION
+
+  eUseCounter_Count
+};
+
+}
+
+#endif

dom/base/UseCounters.conf

@@ -0,0 +1,63 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// This file defines a list of use counters, which are things that can
+// record usage of Web platform features and then report this information
+// through Telemetry.
+//
+// The format of this file is very strict.  Each line can be:
+//
+//   (a) a blank line
+//
+//   (b) a comment, which is a line that begins with "//"
+//
+//   (c) one of three possible use counter declarations:
+//
+//         method <IDL interface name>.<IDL operation name>
+//         attribute <IDL interface name>.<IDL attribute name>
+//         property <CSS property method name>
+//
+// The |CSS property method name| should be identical to the |method|
+// argument to CSS_PROP and related macros.  The method name is
+// identical to the name of the property, except that all hyphens are
+// removed and CamelCase naming is used.  See nsCSSPropList.h for
+// further details.
+//
+// To actually cause use counters to be incremented, DOM methods
+// and attributes must have a [UseCounter] extended attribute in
+// the Web IDL file.  CSS properties require no special treatment
+// beyond being listed below.
+//
+// You might reasonably ask why we have this file and we require
+// annotating things with [UseCounter] in the relevant WebIDL file as
+// well.  Generating things from bindings codegen and ensuring all the
+// dependencies were correct would have been rather difficult, and
+// annotating the WebIDL files does nothing for identifying CSS
+// property usage, which we would also like to track.
+
+method SVGSVGElement.getElementById
+attribute SVGSVGElement.currentScale
+property Fill
+property FillOpacity
+
+// Push API
+method PushManager.subscribe
+method PushSubscription.unsubscribe
+
+// window.sidebar.addSearchEngine
+attribute Window.sidebar
+method External.addSearchEngine
+
+// AppCache API
+method OfflineResourceList.swapCache
+method OfflineResourceList.update
+attribute OfflineResourceList.status
+attribute OfflineResourceList.onchecking
+attribute OfflineResourceList.onerror
+attribute OfflineResourceList.onnoupdate
+attribute OfflineResourceList.ondownloading
+attribute OfflineResourceList.onprogress
+attribute OfflineResourceList.onupdateready
+attribute OfflineResourceList.oncached
+attribute OfflineResourceList.onobsolete

dom/base/gen-usecounters.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import print_function
+
+import json
+import os
+import sys
+sys.path.append(os.path.dirname(__file__))
+
+import usecounters
+
+AUTOGENERATED_WARNING_COMMENT = "/* THIS FILE IS AUTOGENERATED BY gen-usecounters.py - DO NOT EDIT */"
+
+def generate_list(f, counters):
+    def print_optional_macro_declare(name):
+        print('''
+#ifndef %(name)s
+#define %(name)s(interface_, name_) // nothing
+#define DEFINED_%(name)s
+#endif
+''' % { 'name': name }, file=f)
+
+    def print_optional_macro_undeclare(name):
+        print('''
+#ifdef DEFINED_%(name)s
+#undef DEFINED_%(name)s
+#undef %(name)s
+#endif
+''' % { 'name': name }, file=f)
+
+    print(AUTOGENERATED_WARNING_COMMENT, file=f)
+
+    print_optional_macro_declare('USE_COUNTER_DOM_METHOD')
+    print_optional_macro_declare('USE_COUNTER_DOM_ATTRIBUTE')
+    print_optional_macro_declare('USE_COUNTER_CSS_PROPERTY')
+
+    for counter in counters:
+        if counter['type'] == 'method':
+            print('USE_COUNTER_DOM_METHOD(%s, %s)' % (counter['interface_name'], counter['method_name']), file=f)
+        elif counter['type'] == 'attribute':
+            print('USE_COUNTER_DOM_ATTRIBUTE(%s, %s)' % (counter['interface_name'], counter['attribute_name']), file=f)
+        elif counter['type'] == 'property':
+            prop = counter['property_name']
+            print('USE_COUNTER_CSS_PROPERTY(%s, %s)' % (prop, prop), file=f)
+
+    print_optional_macro_undeclare('USE_COUNTER_DOM_METHOD')
+    print_optional_macro_undeclare('USE_COUNTER_DOM_ATTRIBUTE')
+    print_optional_macro_undeclare('USE_COUNTER_CSS_PROPERTY')
+
+def generate_property_map(f, counters):
+    print(AUTOGENERATED_WARNING_COMMENT, file=f)
+    print('''
+enum {
+  #define CSS_PROP_PUBLIC_OR_PRIVATE(publicname_, privatename_) privatename_
+  #define CSS_PROP_LIST_INCLUDE_LOGICAL
+  #define CSS_PROP(name_, id_, method_, flags_, pref_, parsevariant_,     \\
+                   kwtable_, stylestruct_, stylestructoffset_, animtype_) \\
+    USE_COUNTER_FOR_CSS_PROPERTY_##method_ = eUseCounter_UNKNOWN,
+  #include "nsCSSPropList.h"
+  #undef CSS_PROP
+  #undef CSS_PROP_LIST_INCLUDE_LOGICAL
+  #undef CSS_PROP_PUBLIC_OR_PRIVATE
+};
+''', file=f)
+    for counter in counters:
+        if counter['type'] == 'property':
+            prop = counter['property_name']
+            print('#define USE_COUNTER_FOR_CSS_PROPERTY_%s eUseCounter_property_%s' % (prop, prop), file=f)
+
+def use_counter_list(output_header, conf_filename):
+    counters = usecounters.read_conf(conf_filename)
+    generate_list(output_header, counters)
+
+def property_map(output_map, conf_filename):
+    counters = usecounters.read_conf(conf_filename)
+    generate_property_map(output_map, counters)

dom/base/moz.build

@@ -141,9 +141,11 @@ EXPORTS.mozilla += [
     'FeedWriterEnabled.h',
     'TextInputProcessor.h',
     'TimerClamping.h',
+    'UseCounter.h',
 ]
 
 EXPORTS.mozilla.dom += [
+    '!UseCounterList.h',
     'AnonymousContent.h',
     'Attr.h',
     'BarProps.h',
@@ -469,5 +471,18 @@ if CONFIG['MOZ_PHOENIX'] or CONFIG['MOZ_XULRUNNER']:
 if CONFIG['MOZ_X11']:
     CXXFLAGS += CONFIG['TK_CFLAGS']
 
+GENERATED_FILES += [
+    'PropertyUseCounterMap.inc',
+    'UseCounterList.h',
+]
+
+countermap = GENERATED_FILES['PropertyUseCounterMap.inc']
+countermap.script = 'gen-usecounters.py:property_map'
+countermap.inputs = ['UseCounters.conf']
+
+counterlist = GENERATED_FILES['UseCounterList.h']
+counterlist.script = 'gen-usecounters.py:use_counter_list'
+counterlist.inputs = ['UseCounters.conf']
+
 if CONFIG['GNU_CXX']:
     CXXFLAGS += ['-Wno-error=shadow']

dom/base/nsDOMWindowUtils.cpp

@@ -104,6 +104,9 @@
 #include "nsContentPermissionHelper.h"
 #include "nsCSSPseudoElements.h"            // for CSSPseudoElementType
 #include "nsNetUtil.h"
+#include "nsDocument.h"
+#include "HTMLImageElement.h"
+#include "mozilla/css/ImageLoader.h"
 #include "mozilla/layers/APZCTreeManager.h" // for layers::ZoomToRectBehavior
 #include "mozilla/dom/Promise.h"
 #include "mozilla/StyleSheetInlines.h"
@@ -4022,6 +4025,27 @@ nsDOMWindowUtils::LeaveChaosMode()
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMWindowUtils::ForceUseCounterFlush(nsIDOMNode *aNode)
+{
+  NS_ENSURE_ARG_POINTER(aNode);
+
+  if (nsCOMPtr<nsIDocument> doc = do_QueryInterface(aNode)) {
+    mozilla::css::ImageLoader* loader = doc->StyleImageLoader();
+    loader->FlushUseCounters();
+    return NS_OK;
+  }
+
+  if (nsCOMPtr<nsIContent> content = do_QueryInterface(aNode)) {
+    if (HTMLImageElement* img = HTMLImageElement::FromContent(content)) {
+      img->FlushUseCounters();
+      return NS_OK;
+    }
+  }
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMWindowUtils::HasRuleProcessorUsedByMultipleStyleSets(uint32_t aSheetType,
                                                           bool* aRetVal)

dom/base/nsDocument.cpp

@@ -9718,6 +9718,19 @@ static const char* kDocumentWarnings[] = {
 };
 #undef DOCUMENT_WARNING
 
+static UseCounter
+OperationToUseCounter(nsIDocument::DeprecatedOperations aOperation)
+{
+  switch(aOperation) {
+#define DEPRECATED_OPERATION(_op) \
+    case nsIDocument::e##_op: return eUseCounter_##_op;
+#include "nsDeprecatedOperationList.h"
+#undef DEPRECATED_OPERATION
+  default:
+    MOZ_CRASH();
+  }
+}
+
 bool
 nsIDocument::HasWarnedAbout(DeprecatedOperations aOperation) const
 {
@@ -9733,6 +9746,7 @@ nsIDocument::WarnOnceAbout(DeprecatedOperations aOperation,
     return;
   }
   mDeprecationWarnedAbout[aOperation] = true;
+  const_cast<nsIDocument*>(this)->SetDocumentAndPageUseCounter(OperationToUseCounter(aOperation));
   uint32_t flags = asError ? nsIScriptError::errorFlag
                            : nsIScriptError::warningFlag;
   nsContentUtils::ReportToConsole(flags,
@@ -11983,6 +11997,69 @@ nsIDocument::GetTopLevelContentDocument()
   return parent;
 }
 
+void
+nsIDocument::PropagateUseCounters(nsIDocument* aParentDocument)
+{
+  MOZ_ASSERT(this != aParentDocument);
+
+  // What really matters here is that our use counters get propagated as
+  // high up in the content document hierarchy as possible.  So,
+  // starting with aParentDocument, we need to find the toplevel content
+  // document, and propagate our use counters into its
+  // mChildDocumentUseCounters.
+  nsIDocument* contentParent = aParentDocument->GetTopLevelContentDocument();
+
+  if (!contentParent) {
+    return;
+  }
+
+  contentParent->mChildDocumentUseCounters |= mUseCounters;
+  contentParent->mChildDocumentUseCounters |= mChildDocumentUseCounters;
+}
+
+void
+nsIDocument::SetPageUseCounter(UseCounter aUseCounter)
+{
+  // We want to set the use counter on the "page" that owns us; the definition
+  // of "page" depends on what kind of document we are.  See the comments below
+  // for details.  In any event, checking all the conditions below is
+  // reasonably expensive, so we cache whether we've notified our owning page.
+  if (mNotifiedPageForUseCounter[aUseCounter]) {
+    return;
+  }
+  mNotifiedPageForUseCounter[aUseCounter] = true;
+
+  if (mDisplayDocument) {
+    // If we are a resource document, we won't have a docshell and so we won't
+    // record any page use counters on this document.  Instead, we should
+    // forward it up to the document that loaded us.
+    MOZ_ASSERT(!mDocumentContainer);
+    mDisplayDocument->SetChildDocumentUseCounter(aUseCounter);
+    return;
+  }
+
+  if (IsBeingUsedAsImage()) {
+    // If this is an SVG image document, we also won't have a docshell.
+    MOZ_ASSERT(!mDocumentContainer);
+    return;
+  }
+
+  // We only care about use counters in content.  If we're already a toplevel
+  // content document, then we should have already set the use counter on
+  // ourselves, and we are done.
+  nsIDocument* contentParent = GetTopLevelContentDocument();
+  if (!contentParent) {
+    return;
+  }
+
+  if (this == contentParent) {
+    MOZ_ASSERT(GetUseCounter(aUseCounter));
+    return;
+  }
+
+  contentParent->SetChildDocumentUseCounter(aUseCounter);
+}
+
 bool
 nsIDocument::HasScriptsBlockedBySandbox()
 {

dom/base/nsIDocument.h

@@ -24,6 +24,7 @@
 #include "nsTHashtable.h"                // for member
 #include "mozilla/net/ReferrerPolicy.h"  // for member
 #include "nsWeakReference.h"
+#include "mozilla/UseCounter.h"
 #include "mozilla/WeakPtr.h"
 #include "Units.h"
 #include "nsContentListDeclarations.h"
@@ -2781,6 +2782,23 @@ public:
 
   bool DidFireDOMContentLoaded() const { return mDidFireDOMContentLoaded; }
 
+  void SetDocumentUseCounter(mozilla::UseCounter aUseCounter)
+  {
+    if (!mUseCounters[aUseCounter]) {
+      mUseCounters[aUseCounter] = true;
+    }
+  }
+
+  void SetPageUseCounter(mozilla::UseCounter aUseCounter);
+
+  void SetDocumentAndPageUseCounter(mozilla::UseCounter aUseCounter)
+  {
+    SetDocumentUseCounter(aUseCounter);
+    SetPageUseCounter(aUseCounter);
+  }
+
+  void PropagateUseCounters(nsIDocument* aParentDocument);
+
   void SetUserHasInteracted(bool aUserHasInteracted)
   {
     mUserHasInteracted = aUserHasInteracted;
@@ -2839,6 +2857,24 @@ public:
 
   virtual void ScheduleResizeObserversNotification() const = 0;
 
+protected:
+  bool GetUseCounter(mozilla::UseCounter aUseCounter)
+  {
+    return mUseCounters[aUseCounter];
+  }
+
+  void SetChildDocumentUseCounter(mozilla::UseCounter aUseCounter)
+  {
+    if (!mChildDocumentUseCounters[aUseCounter]) {
+      mChildDocumentUseCounters[aUseCounter] = true;
+    }
+  }
+
+  bool GetChildDocumentUseCounter(mozilla::UseCounter aUseCounter)
+  {
+    return mChildDocumentUseCounters[aUseCounter];
+  }
+
 private:
   mutable std::bitset<eDeprecatedOperationCount> mDeprecationWarnedAbout;
   mutable std::bitset<eDocumentWarningCount> mDocWarningWarnedAbout;
@@ -3279,7 +3315,15 @@ protected:
   // Our live MediaQueryLists
   PRCList mDOMMediaQueryLists;
 
- // Whether the user has interacted with the document or not:
+  // Flags for use counters used directly by this document.
+  std::bitset<mozilla::eUseCounter_Count> mUseCounters;
+  // Flags for use counters used by any child documents of this document.
+  std::bitset<mozilla::eUseCounter_Count> mChildDocumentUseCounters;
+  // Flags for whether we've notified our top-level "page" of a use counter
+  // for this child document.
+  std::bitset<mozilla::eUseCounter_Count> mNotifiedPageForUseCounter;
+
+  // Whether the user has interacted with the document or not:
   bool mUserHasInteracted;
 
   mozilla::TimeStamp mPageUnloadingEventTimeStamp;

dom/base/nsImageLoadingContent.cpp

@@ -198,6 +198,12 @@ nsImageLoadingContent::Notify(imgIRequest* aRequest,
   }
 
   if (aType == imgINotificationObserver::DECODE_COMPLETE) {
+    nsCOMPtr<imgIContainer> container;
+    aRequest->GetImage(getter_AddRefs(container));
+    if (container) {
+      container->PropagateUseCounters(GetOurOwnerDoc());
+    }
+
     UpdateImageState(true);
   }
 

dom/base/test/browser.ini

@@ -4,6 +4,13 @@ support-files =
   file_bug1011748_redirect.sjs
   file_bug1011748_OK.sjs
   file_messagemanager_unload.html
+  file_use_counter_outer.html
+  file_use_counter_svg_getElementById.svg
+  file_use_counter_svg_currentScale.svg
+  file_use_counter_svg_fill_pattern_definition.svg
+  file_use_counter_svg_fill_pattern.svg
+  file_use_counter_svg_fill_pattern_internal.svg
+  file_use_counter_svg_fill_pattern_data.svg
 
 [browser_bug593387.js]
 [browser_bug902350.js]
@@ -17,4 +24,5 @@ tags = mcb
 skip-if = e10s # this tests non-e10s behavior. it's not expected to work in e10s.
 [browser_state_notifications.js]
 skip-if = true # Bug 1271028
+[browser_use_counters.js]
 [browser_bug1307747.js]

dom/base/test/browser_use_counters.js

@@ -0,0 +1,305 @@
+/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; js-indent-level: 2 -*- */
+
+requestLongerTimeout(2);
+
+var {Promise: promise} = Cu.import("resource://gre/modules/Promise.jsm", {});
+Cu.import("resource://gre/modules/Services.jsm");
+
+const gHttpTestRoot = "http://example.com/browser/dom/base/test/";
+
+/**
+ * Enable local telemetry recording for the duration of the tests.
+ */
+var gOldContentCanRecord = false;
+var gOldParentCanRecord = false;
+add_task(function* test_initialize() {
+  let Telemetry = Cc["@mozilla.org/base/telemetry;1"].getService(Ci.nsITelemetry);
+  gOldParentCanRecord = Telemetry.canRecordExtended
+  Telemetry.canRecordExtended = true;
+
+  // Because canRecordExtended is a per-process variable, we need to make sure
+  // that all of the pages load in the same content process. Limit the number
+  // of content processes to at most 1 (or 0 if e10s is off entirely).
+  yield SpecialPowers.pushPrefEnv({ set: [[ "dom.ipc.processCount", 1 ]] });
+
+  gOldContentCanRecord = yield ContentTask.spawn(gBrowser.selectedBrowser, {}, function () {
+    let telemetry = Cc["@mozilla.org/base/telemetry;1"].getService(Ci.nsITelemetry);
+    let old = telemetry.canRecordExtended;
+    telemetry.canRecordExtended = true;
+    return old;
+  });
+  info("canRecord for content: " + gOldContentCanRecord);
+});
+
+add_task(function* () {
+  // Check that use counters are incremented by SVGs loaded directly in iframes.
+  yield check_use_counter_iframe("file_use_counter_svg_getElementById.svg",
+                                 "SVGSVGELEMENT_GETELEMENTBYID");
+  yield check_use_counter_iframe("file_use_counter_svg_currentScale.svg",
+                                 "SVGSVGELEMENT_CURRENTSCALE_getter");
+  yield check_use_counter_iframe("file_use_counter_svg_currentScale.svg",
+                                 "SVGSVGELEMENT_CURRENTSCALE_setter");
+
+  // Check that even loads from the imglib cache update use counters.  The
+  // images should still be there, because we just loaded them in the last
+  // set of tests.  But we won't get updated counts for the document
+  // counters, because we won't be re-parsing the SVG documents.
+  yield check_use_counter_iframe("file_use_counter_svg_getElementById.svg",
+                                 "SVGSVGELEMENT_GETELEMENTBYID", false);
+  yield check_use_counter_iframe("file_use_counter_svg_currentScale.svg",
+                                 "SVGSVGELEMENT_CURRENTSCALE_getter", false);
+  yield check_use_counter_iframe("file_use_counter_svg_currentScale.svg",
+                                 "SVGSVGELEMENT_CURRENTSCALE_setter", false);
+
+  // Check that use counters are incremented by SVGs loaded as images.
+  // Note that SVG images are not permitted to execute script, so we can only
+  // check for properties here.
+  yield check_use_counter_img("file_use_counter_svg_getElementById.svg",
+                              "PROPERTY_FILL");
+  yield check_use_counter_img("file_use_counter_svg_currentScale.svg",
+                              "PROPERTY_FILL");
+
+  // Check that use counters are incremented by directly loading SVGs
+  // that reference patterns defined in another SVG file.
+  yield check_use_counter_direct("file_use_counter_svg_fill_pattern.svg",
+                                 "PROPERTY_FILLOPACITY", /*xfail=*/true);
+
+  // Check that use counters are incremented by directly loading SVGs
+  // that reference patterns defined in the same file or in data: URLs.
+  yield check_use_counter_direct("file_use_counter_svg_fill_pattern_internal.svg",
+                                 "PROPERTY_FILLOPACITY");
+  // data: URLs don't correctly propagate to their referring document yet.
+  //yield check_use_counter_direct("file_use_counter_svg_fill_pattern_data.svg",
+  //                               "PROPERTY_FILL_OPACITY");
+});
+
+add_task(function* () {
+  let Telemetry = Cc["@mozilla.org/base/telemetry;1"].getService(Ci.nsITelemetry);
+  Telemetry.canRecordExtended = gOldParentCanRecord;
+
+  yield ContentTask.spawn(gBrowser.selectedBrowser, { oldCanRecord: gOldContentCanRecord }, function (arg) {
+    Cu.import("resource://gre/modules/PromiseUtils.jsm");
+    yield new Promise(resolve => {
+      let telemetry = Cc["@mozilla.org/base/telemetry;1"].getService(Ci.nsITelemetry);
+      telemetry.canRecordExtended = arg.oldCanRecord;
+      resolve();
+    });
+  });
+});
+
+
+function waitForDestroyedDocuments() {
+  let deferred = promise.defer();
+  SpecialPowers.exactGC(deferred.resolve);
+  return deferred.promise;
+}
+
+function waitForPageLoad(browser) {
+  return ContentTask.spawn(browser, null, function*() {
+    Cu.import("resource://gre/modules/PromiseUtils.jsm");
+    yield new Promise(resolve => {
+      let listener = () => {
+        removeEventListener("load", listener, true);
+        resolve();
+      }
+      addEventListener("load", listener, true);
+    });
+  });
+}
+
+function grabHistogramsFromContent(use_counter_middlefix, page_before = null) {
+  let telemetry = Cc["@mozilla.org/base/telemetry;1"].getService(Ci.nsITelemetry);
+  let suffix = Services.appinfo.browserTabsRemoteAutostart ? "#content" : "";
+  let gather = () => [
+    telemetry.getHistogramById("USE_COUNTER2_" + use_counter_middlefix + "_PAGE" + suffix).snapshot().sum,
+    telemetry.getHistogramById("USE_COUNTER2_" + use_counter_middlefix + "_DOCUMENT" + suffix).snapshot().sum,
+    telemetry.getHistogramById("CONTENT_DOCUMENTS_DESTROYED" + suffix).snapshot().sum,
+    telemetry.getHistogramById("TOP_LEVEL_CONTENT_DOCUMENTS_DESTROYED" + suffix).snapshot().sum,
+  ];
+  return BrowserTestUtils.waitForCondition(() => {
+    return page_before != telemetry.getHistogramById("USE_COUNTER2_" + use_counter_middlefix + "_PAGE" + suffix).snapshot().sum;
+  }).then(gather, gather);
+}
+
+var check_use_counter_iframe = Task.async(function* (file, use_counter_middlefix, check_documents=true) {
+  info("checking " + file + " with histogram " + use_counter_middlefix);
+
+  let newTab = gBrowser.addTab( "about:blank");
+  gBrowser.selectedTab = newTab;
+  newTab.linkedBrowser.stop();
+
+  // Hold on to the current values of the telemetry histograms we're
+  // interested in.
+  let [histogram_page_before, histogram_document_before,
+       histogram_docs_before, histogram_toplevel_docs_before] =
+      yield grabHistogramsFromContent(use_counter_middlefix);
+
+  gBrowser.selectedBrowser.loadURI(gHttpTestRoot + "file_use_counter_outer.html");
+  yield waitForPageLoad(gBrowser.selectedBrowser);
+
+  // Inject our desired file into the iframe of the newly-loaded page.
+  yield ContentTask.spawn(gBrowser.selectedBrowser, { file: file }, function(opts) {
+    Cu.import("resource://gre/modules/PromiseUtils.jsm");
+    let deferred = PromiseUtils.defer();
+
+    let wu = content.window.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+
+    let iframe = content.document.getElementById('content');
+    iframe.src = opts.file;
+    let listener = (event) => {
+      event.target.removeEventListener("load", listener, true);
+
+      // We flush the main document first, then the iframe's document to
+      // ensure any propagation that might happen from content->parent should
+      // have already happened when counters are reported to telemetry.
+      wu.forceUseCounterFlush(content.document);
+      wu.forceUseCounterFlush(iframe.contentDocument);
+
+      deferred.resolve();
+    };
+    iframe.addEventListener("load", listener, true);
+
+    return deferred.promise;
+  });
+  
+  // Tear down the page.
+  gBrowser.removeTab(newTab);
+
+  // The histograms only get recorded when the document actually gets
+  // destroyed, which might not have happened yet due to GC/CC effects, etc.
+  // Try to force document destruction.
+  yield waitForDestroyedDocuments();
+
+  // Grab histograms again and compare.
+  let [histogram_page_after, histogram_document_after,
+       histogram_docs_after, histogram_toplevel_docs_after] =
+      yield grabHistogramsFromContent(use_counter_middlefix, histogram_page_before);
+
+  is(histogram_page_after, histogram_page_before + 1,
+     "page counts for " + use_counter_middlefix + " after are correct");
+  ok(histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+     "top level document counts are correct");
+  if (check_documents) {
+    is(histogram_document_after, histogram_document_before + 1,
+       "document counts for " + use_counter_middlefix + " after are correct");
+  }
+});
+
+var check_use_counter_img = Task.async(function* (file, use_counter_middlefix) {
+  info("checking " + file + " as image with histogram " + use_counter_middlefix);
+
+  let newTab = gBrowser.addTab("about:blank");
+  gBrowser.selectedTab = newTab;
+  newTab.linkedBrowser.stop();
+
+  // Hold on to the current values of the telemetry histograms we're
+  // interested in.
+  let [histogram_page_before, histogram_document_before,
+       histogram_docs_before, histogram_toplevel_docs_before] =
+      yield grabHistogramsFromContent(use_counter_middlefix);
+
+  gBrowser.selectedBrowser.loadURI(gHttpTestRoot + "file_use_counter_outer.html");
+  yield waitForPageLoad(gBrowser.selectedBrowser);
+
+  // Inject our desired file into the img of the newly-loaded page.
+  yield ContentTask.spawn(gBrowser.selectedBrowser, { file: file }, function(opts) {
+    Cu.import("resource://gre/modules/PromiseUtils.jsm");
+    let deferred = PromiseUtils.defer();
+
+    let img = content.document.getElementById('display');
+    img.src = opts.file;
+    let listener = (event) => {
+      img.removeEventListener("load", listener, true);
+
+      // Flush for the image.  It matters what order we do these in, so that
+      // the image can propagate its use counters to the document prior to the
+      // document reporting its use counters.
+      let wu = content.window.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+      wu.forceUseCounterFlush(img);
+
+      // Flush for the main window.
+      wu.forceUseCounterFlush(content.document);
+
+      deferred.resolve();
+    };
+    img.addEventListener("load", listener, true);
+
+    return deferred.promise;
+  });
+  
+  // Tear down the page.
+  gBrowser.removeTab(newTab);
+
+  // The histograms only get recorded when the document actually gets
+  // destroyed, which might not have happened yet due to GC/CC effects, etc.
+  // Try to force document destruction.
+  yield waitForDestroyedDocuments();
+
+  // Grab histograms again and compare.
+  let [histogram_page_after, histogram_document_after,
+       histogram_docs_after, histogram_toplevel_docs_after] =
+      yield grabHistogramsFromContent(use_counter_middlefix, histogram_page_before);
+  is(histogram_page_after, histogram_page_before + 1,
+     "page counts for " + use_counter_middlefix + " after are correct");
+  is(histogram_document_after, histogram_document_before + 1,
+     "document counts for " + use_counter_middlefix + " after are correct");
+  ok(histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+     "top level document counts are correct");
+  // 2 documents: one for the outer html page containing the <img> element, and
+  // one for the SVG image itself.
+  ok(histogram_docs_after >= histogram_docs_before + 2,
+     "document counts are correct");
+});
+
+var check_use_counter_direct = Task.async(function* (file, use_counter_middlefix, xfail=false) {
+  info("checking " + file + " with histogram " + use_counter_middlefix);
+
+  let newTab = gBrowser.addTab( "about:blank");
+  gBrowser.selectedTab = newTab;
+  newTab.linkedBrowser.stop();
+
+  // Hold on to the current values of the telemetry histograms we're
+  // interested in.
+  let [histogram_page_before, histogram_document_before,
+       histogram_docs_before, histogram_toplevel_docs_before] =
+      yield grabHistogramsFromContent(use_counter_middlefix);
+
+  gBrowser.selectedBrowser.loadURI(gHttpTestRoot + file);
+  yield ContentTask.spawn(gBrowser.selectedBrowser, null, function*() {
+    Cu.import("resource://gre/modules/PromiseUtils.jsm");
+    yield new Promise(resolve => {
+      let listener = () => {
+        removeEventListener("load", listener, true);
+
+        let wu = content.window.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+        wu.forceUseCounterFlush(content.document);
+
+        setTimeout(resolve, 0);
+      }
+      addEventListener("load", listener, true);
+    });
+  });
+  
+  // Tear down the page.
+  gBrowser.removeTab(newTab);
+
+  // The histograms only get recorded when the document actually gets
+  // destroyed, which might not have happened yet due to GC/CC effects, etc.
+  // Try to force document destruction.
+  yield waitForDestroyedDocuments();
+
+  // Grab histograms again and compare.
+  let [histogram_page_after, histogram_document_after,
+       histogram_docs_after, histogram_toplevel_docs_after] =
+      yield grabHistogramsFromContent(use_counter_middlefix, histogram_page_before);
+  if (!xfail) {
+    is(histogram_page_after, histogram_page_before + 1,
+       "page counts for " + use_counter_middlefix + " after are correct");
+    is(histogram_document_after, histogram_document_before + 1,
+       "document counts for " + use_counter_middlefix + " after are correct");
+  }
+  ok(histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+     "top level document counts are correct");
+  ok(histogram_docs_after >= histogram_docs_before + 1,
+     "document counts are correct");
+});

dom/base/test/file_use_counter_outer.html

@@ -0,0 +1,17 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=968923
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 968923</title>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=968923">Mozilla Bug 968923</a>
+<img id="display" />
+<iframe id="content">
+
+</iframe>
+</body>
+</html>

dom/base/test/file_use_counter_svg_currentScale.svg

@@ -0,0 +1,17 @@
+<?xml version="1.0" standalone="no"?>
+
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="4in" height="3in" version="1.1"
+     xmlns="http://www.w3.org/2000/svg"
+     xmlns:xlink="http://www.w3.org/1999/xlink">
+  <desc>Test graphic for hitting currentScale
+  </desc>
+  <script type="text/javascript"> <![CDATA[
+    document.documentElement.currentScale = document.documentElement.currentScale;
+    ]]>
+  </script>
+  <image id="i1" x="200" y="200" width="100px" height="80px">
+  </image>
+  <circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="red"/>
+</svg>

dom/base/test/file_use_counter_svg_fill_pattern.svg

@@ -0,0 +1,15 @@
+<?xml version="1.0" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
+  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="8cm" height="4cm" viewBox="0 0 800 400" version="1.1"
+     xmlns="http://www.w3.org/2000/svg">
+  <desc>Borrowed from http://www.w3.org/TR/SVG/pservers.html</desc>
+  <!-- Outline the drawing area in blue -->
+  <rect fill="none" stroke="blue" 
+        x="1" y="1" width="798" height="398"/>
+
+  <!-- The ellipse is filled using a triangle pattern paint server
+       and stroked with black -->
+  <ellipse fill="url(http://example.com/browser/dom/base/test/file_use_counter_svg_fill_pattern_definition.svg#TrianglePattern)" stroke="black" stroke-width="5"  
+           cx="400" cy="200" rx="350" ry="150" />
+</svg>

dom/base/test/file_use_counter_svg_fill_pattern_data.svg

@@ -0,0 +1,15 @@
+<?xml version="1.0" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
+  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="8cm" height="4cm" viewBox="0 0 800 400" version="1.1"
+     xmlns="http://www.w3.org/2000/svg">
+  <desc>Borrowed from http://www.w3.org/TR/SVG/pservers.html</desc>
+  <!-- Outline the drawing area in blue -->
+  <rect fill="none" stroke="blue" 
+        x="1" y="1" width="798" height="398"/>
+
+  <!-- The ellipse is filled using a triangle pattern paint server
+       and stroked with black -->
+  <ellipse fill="url(data:image/svg+xml;base64,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#TrianglePattern)" stroke="black" stroke-width="5"  
+           cx="400" cy="200" rx="350" ry="150" />
+</svg>

dom/base/test/file_use_counter_svg_fill_pattern_definition.svg

@@ -0,0 +1,14 @@
+<?xml version="1.0" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
+  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="8cm" height="4cm" viewBox="0 0 800 400" version="1.1"
+     xmlns="http://www.w3.org/2000/svg">
+  <desc>Borrowed from http://www.w3.org/TR/SVG/pservers.html</desc>
+  <defs>
+    <pattern id="TrianglePattern" patternUnits="userSpaceOnUse"
+             x="0" y="0" width="100" height="100"
+             viewBox="0 0 10 10" >
+      <path d="M 0 0 L 7 0 L 3.5 7 z" fill="red" fill-opacity="0.7" stroke="blue" />
+    </pattern> 
+  </defs>
+</svg>

dom/base/test/file_use_counter_svg_fill_pattern_internal.svg

@@ -0,0 +1,23 @@
+<?xml version="1.0" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
+  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="8cm" height="4cm" viewBox="0 0 800 400" version="1.1"
+     xmlns="http://www.w3.org/2000/svg">
+  <desc>Borrowed from http://www.w3.org/TR/SVG/pservers.html</desc>
+  <!-- Outline the drawing area in blue -->
+  <rect fill="none" stroke="blue" 
+        x="1" y="1" width="798" height="398"/>
+
+  <defs>
+    <pattern id="TrianglePattern" patternUnits="userSpaceOnUse"
+             x="0" y="0" width="100" height="100"
+             viewBox="0 0 10 10" >
+      <path d="M 0 0 L 7 0 L 3.5 7 z" fill="red" fill-opacity="0.7" stroke="blue" />
+    </pattern> 
+  </defs>
+
+  <!-- The ellipse is filled using a triangle pattern paint server
+       and stroked with black -->
+  <ellipse fill="url(#TrianglePattern)" stroke="black" stroke-width="5"  
+           cx="400" cy="200" rx="350" ry="150" />
+</svg>

dom/base/test/file_use_counter_svg_getElementById.svg

@@ -0,0 +1,22 @@
+<?xml version="1.0" standalone="no"?>
+
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg width="4in" height="3in" version="1.1"
+     xmlns="http://www.w3.org/2000/svg"
+     xmlns:xlink="http://www.w3.org/1999/xlink">
+  <desc>Test graphic for hitting getElementById
+  </desc>
+  <image id="i1" x="200" y="200" width="100px" height="80px">
+  </image>
+  <circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="red"/>
+  <script type="text/javascript"> <![CDATA[
+    var image = document.documentElement.getElementById("i1");
+    image.addEventListener("load",
+                           function() {
+                            document.documentElement.removeAttribute("class");
+                           },
+                           false);
+    ]]>
+  </script>
+</svg>

dom/base/usecounters.py

@@ -0,0 +1,71 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import buildconfig
+import collections
+import re
+import StringIO
+import sys
+
+def read_conf(conf_filename):
+    # Can't read/write from a single StringIO, so make a new one for reading.
+    stream = open(conf_filename, 'rU')
+
+    def parse_counters(stream):
+        for line_num, line in enumerate(stream):
+            line = line.rstrip('\n')
+            if not line or line.startswith('//'):
+                # empty line or comment
+                continue
+            m = re.match(r'method ([A-Za-z0-9]+)\.([A-Za-z0-9]+)$', line)
+            if m:
+                interface_name, method_name = m.groups()
+                yield { 'type': 'method',
+                        'interface_name': interface_name,
+                        'method_name': method_name }
+                continue
+            m = re.match(r'attribute ([A-Za-z0-9]+)\.([A-Za-z0-9]+)$', line)
+            if m:
+                interface_name, attribute_name = m.groups()
+                yield { 'type': 'attribute',
+                        'interface_name': interface_name,
+                        'attribute_name': attribute_name }
+                continue
+            m = re.match(r'property ([A-Za-z0-9]+)$', line)
+            if m:
+                property_name = m.group(1)
+                yield { 'type': 'property',
+                        'property_name': property_name }
+                continue
+            raise ValueError('error parsing %s at line %d' % (conf_filename, line_num))
+
+    return parse_counters(stream)
+
+def generate_histograms(filename):
+    # The mapping for use counters to telemetry histograms depends on the
+    # ordering of items in the dictionary.
+    items = collections.OrderedDict()
+    for counter in read_conf(filename):
+        def append_counter(name, desc):
+            items[name] = { 'expires_in_version': 'never',
+                            'kind' : 'boolean',
+                            'description': desc }
+
+        def append_counters(name, desc):
+            append_counter('USE_COUNTER2_%s_DOCUMENT' % name, 'Whether a document %s' % desc)
+            append_counter('USE_COUNTER2_%s_PAGE' % name, 'Whether a page %s' % desc)
+
+        if counter['type'] == 'method':
+            method = '%s.%s' % (counter['interface_name'], counter['method_name'])
+            append_counters(method.replace('.', '_').upper(), 'called %s' % method)
+        elif counter['type'] == 'attribute':
+            attr = '%s.%s' % (counter['interface_name'], counter['attribute_name'])
+            counter_name = attr.replace('.', '_').upper()
+            append_counters('%s_getter' % counter_name, 'got %s' % attr)
+            append_counters('%s_setter' % counter_name, 'set %s' % attr)
+        elif counter['type'] == 'property':
+            prop = counter['property_name']
+            append_counters('PROPERTY_%s' % prop.replace('-', '_').upper(), "used the '%s' property" % prop)
+
+    return items

dom/bindings/BindingUtils.cpp

@@ -14,6 +14,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/SizePrintfMacros.h"
 #include "mozilla/Unused.h"
+#include "mozilla/UseCounter.h"
 #include "mozilla/dom/DocGroup.h"
 
 #include "AccessCheck.h"
@@ -58,6 +59,7 @@
 #include "mozilla/jsipc/CrossProcessObjectWrappers.h"
 #include "nsDOMClassInfo.h"
 #include "ipc/ErrorIPCUtils.h"
+#include "mozilla/UseCounter.h"
 
 namespace mozilla {
 namespace dom {
@@ -3590,6 +3592,16 @@ AssertReflectorHasGivenProto(JSContext* aCx, JSObject* aReflector,
 } // namespace binding_detail
 #endif // DEBUG
 
+void
+SetDocumentAndPageUseCounter(JSContext* aCx, JSObject* aObject,
+                             UseCounter aUseCounter)
+{
+  nsGlobalWindow* win = xpc::WindowGlobalOrNull(js::UncheckedUnwrap(aObject));
+  if (win && win->GetDocument()) {
+    win->GetDocument()->SetDocumentAndPageUseCounter(aUseCounter);
+  }
+}
+
 namespace {
 
 // This runnable is used to write a deprecation message from a worker to the

dom/bindings/BindingUtils.h

@@ -46,6 +46,8 @@ class nsIJSID;
 
 namespace mozilla {
 
+enum UseCounter : int16_t;
+
 namespace dom {
 class CustomElementReactionsStack;
 template<typename KeyType, typename ValueType> class Record;
@@ -3426,6 +3428,10 @@ already_AddRefed<nsGenericHTMLElement>
 CreateHTMLElement(const GlobalObject& aGlobal, const JS::CallArgs& aCallArgs,
                   JS::Handle<JSObject*> aGivenProto, ErrorResult& aRv);
 
+void
+SetDocumentAndPageUseCounter(JSContext* aCx, JSObject* aObject,
+                             UseCounter aUseCounter);
+
 // Warnings
 void
 DeprecationWarning(JSContext* aCx, JSObject* aObject,

dom/bindings/Codegen.py

@@ -7467,8 +7467,8 @@ class CGPerSignatureCall(CGThing):
 
     def __init__(self, returnType, arguments, nativeMethodName, static,
                  descriptor, idlNode, argConversionStartsAt=0, getter=False,
-                 setter=False, isConstructor=False, resultVar=None,
-                 objectName="obj"):
+                 setter=False, isConstructor=False, useCounterName=None,
+                 resultVar=None, objectName="obj"):
         assert idlNode.isMethod() == (not getter and not setter)
         assert idlNode.isAttr() == (getter or setter)
         # Constructors are always static
@@ -7701,6 +7701,11 @@ class CGPerSignatureCall(CGThing):
                 nativeMethodName,
                 static, argsPost=argsPost, resultVar=resultVar))
 
+        if useCounterName:
+            # Generate a telemetry call for when [UseCounter] is used.
+            code = "SetDocumentAndPageUseCounter(cx, obj, eUseCounter_%s);\n" % useCounterName
+            cgThings.append(CGGeneric(code))
+
         self.cgRoot = CGList(cgThings)
 
     def getArguments(self):
@@ -7929,6 +7934,11 @@ class CGMethodCall(CGThing):
             methodName = "%s.%s" % (descriptor.interface.identifier.name, method.identifier.name)
         argDesc = "argument %d of " + methodName
 
+        if method.getExtendedAttribute("UseCounter"):
+            useCounterName = methodName.replace(".", "_")
+        else:
+            useCounterName = None
+
         if method.isStatic():
             nativeType = descriptor.nativeType
             staticTypeOverride = PropertyDefiner.getStringAttr(method, "StaticClassOverride")
@@ -7950,7 +7960,8 @@ class CGMethodCall(CGThing):
                                       nativeMethodName, static, descriptor,
                                       method,
                                       argConversionStartsAt=argConversionStartsAt,
-                                      isConstructor=isConstructor)
+                                      isConstructor=isConstructor,
+                                      useCounterName=useCounterName)
 
         signatures = method.signatures()
         if len(signatures) == 1:
@@ -8326,11 +8337,16 @@ class CGGetterCall(CGPerSignatureCall):
     getter.
     """
     def __init__(self, returnType, nativeMethodName, descriptor, attr):
+        if attr.getExtendedAttribute("UseCounter"):
+            useCounterName = "%s_%s_getter" % (descriptor.interface.identifier.name,
+                                               attr.identifier.name)
+        else:
+            useCounterName = None
         if attr.isStatic():
             nativeMethodName = "%s::%s" % (descriptor.nativeType, nativeMethodName)
         CGPerSignatureCall.__init__(self, returnType, [], nativeMethodName,
                                     attr.isStatic(), descriptor, attr,
-                                    getter=True)
+                                    getter=True, useCounterName=useCounterName)
 
 
 class CGNavigatorGetterCall(CGPerSignatureCall):
@@ -8397,12 +8413,17 @@ class CGSetterCall(CGPerSignatureCall):
     setter.
     """
     def __init__(self, argType, nativeMethodName, descriptor, attr):
+        if attr.getExtendedAttribute("UseCounter"):
+            useCounterName = "%s_%s_setter" % (descriptor.interface.identifier.name,
+                                               attr.identifier.name)
+        else:
+            useCounterName = None
         if attr.isStatic():
             nativeMethodName = "%s::%s" % (descriptor.nativeType, nativeMethodName)
         CGPerSignatureCall.__init__(self, None,
                                     [FakeArgument(argType, attr, allowTreatNonCallableAsNull=True)],
                                     nativeMethodName, attr.isStatic(),
-                                    descriptor, attr, setter=True)
+                                    descriptor, attr, setter=True, useCounterName=useCounterName)
 
     def wrap_return_value(self):
         attr = self.idlNode
@@ -13911,6 +13932,12 @@ class CGBindingRoot(CGThing):
             bindingHeaders[CGHeaders.getDeclarationFilename(enums[0])] = True
             bindingHeaders["jsapi.h"] = True
 
+        # For things that have [UseCounter]
+        def descriptorRequiresTelemetry(desc):
+            iface = desc.interface
+            return any(m.getExtendedAttribute("UseCounter") for m in iface.members)
+        bindingHeaders["mozilla/UseCounter.h"] = any(
+            descriptorRequiresTelemetry(d) for d in descriptors)
         bindingHeaders["mozilla/dom/SimpleGlobalObject.h"] = any(
             CGDictionary.dictionarySafeToJSONify(d) for d in dictionaries)
         bindingHeaders["XrayWrapper.h"] = any(

dom/bindings/parser/WebIDL.py

@@ -4245,6 +4245,11 @@ class IDLAttribute(IDLInterfaceMember):
                                   "readonly attributes" % attr.value(),
                                   [attr.location, self.location])
             self._setDependsOn(attr.value())
+        elif identifier == "UseCounter":
+            if self.stringifier:
+                raise WebIDLError("[UseCounter] must not be used on a "
+                                  "stringifier attribute",
+                                  [attr.location, self.location])
         elif identifier == "Unscopable":
             if not attr.noArguments():
                 raise WebIDLError("[Unscopable] must take no arguments",
@@ -4974,6 +4979,11 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
                 raise WebIDLError("[Alias] takes an identifier or string",
                                   [attr.location])
             self._addAlias(attr.value())
+        elif identifier == "UseCounter":
+            if self.isSpecial():
+                raise WebIDLError("[UseCounter] must not be used on a special "
+                                  "operation",
+                                  [attr.location, self.location])
         elif identifier == "Unscopable":
             if not attr.noArguments():
                 raise WebIDLError("[Unscopable] must take no arguments",

dom/html/HTMLImageElement.cpp

@@ -10,6 +10,7 @@
 #include "nsPresContext.h"
 #include "nsMappedAttributes.h"
 #include "nsSize.h"
+#include "nsDocument.h"
 #include "nsIDocument.h"
 #include "nsIDOMMutationEvent.h"
 #include "nsIScriptContext.h"
@@ -26,6 +27,7 @@
 #include "mozilla/dom/HTMLFormElement.h"
 #include "nsAttrValueOrString.h"
 #include "imgLoader.h"
+#include "Image.h"
 
 // Responsive images!
 #include "mozilla/dom/HTMLSourceElement.h"
@@ -1360,6 +1362,16 @@ HTMLImageElement::MediaFeatureValuesChanged()
   QueueImageLoadTask(false);
 }
 
+void
+HTMLImageElement::FlushUseCounters()
+{
+  nsCOMPtr<imgIRequest> request;
+  GetRequest(CURRENT_REQUEST, getter_AddRefs(request));
+
+  nsCOMPtr<imgIContainer> container;
+  request->GetImage(getter_AddRefs(container));
+}
+
 } // namespace dom
 } // namespace mozilla
 

dom/html/HTMLImageElement.h

@@ -261,6 +261,12 @@ public:
                                 const nsAString& aMediaAttr,
                                 nsAString& aResult);
 
+  /**
+   * If this image's src pointers to an SVG document, flush the SVG document's
+   * use counters to telemetry.  Only used for testing purposes.
+   */
+  void FlushUseCounters();
+
 protected:
   virtual ~HTMLImageElement();
 

dom/interfaces/base/nsIDOMWindowUtils.idl

@@ -49,7 +49,7 @@ interface nsIJSRAIIHelper;
 interface nsIContentPermissionRequest;
 interface nsIObserver;
 
-[scriptable, uuid(7fcc7958-77d9-45ff-8c81-277bde5f0dc8)]
+[scriptable, uuid(c471d440-004b-4c50-a6f2-747db5f443b6)]
 interface nsIDOMWindowUtils : nsISupports {
 
   /**
@@ -1938,6 +1938,17 @@ interface nsIDOMWindowUtils : nsISupports {
    */
   bool hasRuleProcessorUsedByMultipleStyleSets(in unsigned long aSheetType);
 
+  /*
+   * Force the use counters for the node's associated document(s) to be
+   * flushed to telemetry.  For example, a document node will flush its own
+   * counters and an image node with an SVG source will flush the SVG
+   * document's counters.  Normally, use counters are flushed to telemetry
+   * upon document destruction, but as document destruction is somewhat
+   * non-deterministic, we have this method here for more determinism when
+   * running tests.
+   */
+  void forceUseCounterFlush(in nsIDOMNode aNode);
+
   void setNextPaintSyncId(in long aSyncId);
 
   /**

dom/svg/nsSVGElement.cpp

@@ -1150,7 +1150,7 @@ public:
   MappedAttrParser(css::Loader* aLoader,
                    nsIURI* aDocURI,
                    already_AddRefed<nsIURI> aBaseURI,
-                   nsIPrincipal* aNodePrincipal);
+                   nsSVGElement* aElement);
   ~MappedAttrParser();
 
   // Parses a mapped attribute value.
@@ -1170,18 +1170,20 @@ private:
   // Arguments for nsCSSParser::ParseProperty
   nsIURI*           mDocURI;
   nsCOMPtr<nsIURI>  mBaseURI;
-  nsIPrincipal*     mNodePrincipal;
 
   // Declaration for storing parsed values (lazily initialized)
   css::Declaration* mDecl;
+
+  // For reporting use counters
+  nsSVGElement*     mElement;
 };
 
 MappedAttrParser::MappedAttrParser(css::Loader* aLoader,
                                    nsIURI* aDocURI,
                                    already_AddRefed<nsIURI> aBaseURI,
-                                   nsIPrincipal* aNodePrincipal)
+                                   nsSVGElement* aElement)
   : mParser(aLoader), mDocURI(aDocURI), mBaseURI(aBaseURI),
-    mNodePrincipal(aNodePrincipal), mDecl(nullptr)
+    mDecl(nullptr), mElement(aElement)
 {
 }
 
@@ -1206,9 +1208,27 @@ MappedAttrParser::ParseMappedAttrValue(nsIAtom* aMappedAttrName,
     nsCSSProps::LookupProperty(nsDependentAtomString(aMappedAttrName),
                                CSSEnabledState::eForAllContent);
   if (propertyID != eCSSProperty_UNKNOWN) {
-    bool changed; // outparam for ParseProperty. (ignored)
+    bool changed = false; // outparam for ParseProperty.
     mParser.ParseProperty(propertyID, aMappedAttrValue, mDocURI, mBaseURI,
-                          mNodePrincipal, mDecl, &changed, false, true);
+                          mElement->NodePrincipal(), mDecl, &changed, false, true);
+    if (changed) {
+      // The normal reporting of use counters by the nsCSSParser won't happen
+      // since it doesn't have a sheet.
+      if (nsCSSProps::IsShorthand(propertyID)) {
+        CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(subprop, propertyID,
+                                             CSSEnabledState::eForAllContent) {
+          UseCounter useCounter = nsCSSProps::UseCounterFor(*subprop);
+          if (useCounter != eUseCounter_UNKNOWN) {
+            mElement->OwnerDoc()->SetDocumentAndPageUseCounter(useCounter);
+          }
+        }
+      } else {
+        UseCounter useCounter = nsCSSProps::UseCounterFor(propertyID);
+        if (useCounter != eUseCounter_UNKNOWN) {
+          mElement->OwnerDoc()->SetDocumentAndPageUseCounter(useCounter);
+        }
+      }
+    }
     return;
   }
   MOZ_ASSERT(aMappedAttrName == nsGkAtoms::lang,
@@ -1255,7 +1275,7 @@ nsSVGElement::UpdateContentStyleRule()
 
   nsIDocument* doc = OwnerDoc();
   MappedAttrParser mappedAttrParser(doc->CSSLoader(), doc->GetDocumentURI(),
-                                    GetBaseURI(), NodePrincipal());
+                                    GetBaseURI(), this);
 
   for (uint32_t i = 0; i < attrCount; ++i) {
     const nsAttrName* attrName = mAttrsAndChildren.AttrNameAt(i);
@@ -1346,7 +1366,7 @@ nsSVGElement::UpdateAnimatedContentStyleRule()
   }
 
   MappedAttrParser mappedAttrParser(doc->CSSLoader(), doc->GetDocumentURI(),
-                                    GetBaseURI(), NodePrincipal());
+                                    GetBaseURI(), this);
   doc->PropertyTable(SMIL_MAPPED_ATTR_ANIMVAL)->
     Enumerate(this, ParseMappedAttrAnimValueCallback, &mappedAttrParser);
  

dom/webidl/External.webidl

@@ -13,7 +13,7 @@ interface External
 
 // Mozilla extension
 partial interface External {
-  [UnsafeInPrerendering]
+  [UnsafeInPrerendering, UseCounter]
   void addSearchEngine(DOMString engineURL, DOMString iconURL,
                        DOMString suggestedTitle, DOMString suggestedCategory);
 };

dom/webidl/OfflineResourceList.webidl

@@ -25,30 +25,38 @@ interface OfflineResourceList : EventTarget {
   /* The application cache group is now obsolete. */
   const unsigned short OBSOLETE = 5;
 
-  [Throws]
+  [Throws, UseCounter]
   readonly attribute unsigned short status;
 
   /**
    * Begin the application update process on the associated application cache.
    */
-  [Throws]
+  [Throws, UseCounter]
   void update();
 
   /**
    * Swap in the newest version of the application cache, or disassociate
    * from the cache if the cache group is obsolete.
    */
-  [Throws]
+  [Throws, UseCounter]
   void swapCache();
 
   /* Events */
+  [UseCounter]
   attribute EventHandler onchecking;
+  [UseCounter]
   attribute EventHandler onerror;
+  [UseCounter]
   attribute EventHandler onnoupdate;
+  [UseCounter]
   attribute EventHandler ondownloading;
+  [UseCounter]
   attribute EventHandler onprogress;
+  [UseCounter]
   attribute EventHandler onupdateready;
+  [UseCounter]
   attribute EventHandler oncached;
+  [UseCounter]
   attribute EventHandler onobsolete;
 };
 

dom/webidl/PushManager.webidl

@@ -25,7 +25,7 @@ interface PushManagerImpl {
 [Exposed=(Window,Worker), Func="nsContentUtils::PushEnabled",
  ChromeConstructor(DOMString scope)]
 interface PushManager {
-  [Throws]
+  [Throws, UseCounter]
   Promise<PushSubscription>    subscribe(optional PushSubscriptionOptionsInit options);
   [Throws]
   Promise<PushSubscription?>   getSubscription();

dom/webidl/PushSubscription.webidl

@@ -44,7 +44,7 @@ interface PushSubscription
   readonly attribute PushSubscriptionOptions options;
   [Throws]
   ArrayBuffer? getKey(PushEncryptionKeyName name);
-  [Throws]
+  [Throws, UseCounter]
   Promise<boolean> unsubscribe();
 
   // Implements the custom serializer specified in Push API, section 9.

dom/webidl/SVGSVGElement.webidl

@@ -33,6 +33,7 @@ interface SVGSVGElement : SVGGraphicsElement {
   readonly attribute float screenPixelToMillimeterY;
   readonly attribute boolean useCurrentView;
   // readonly attribute SVGViewSpec currentView;
+  [UseCounter]
            attribute float currentScale;
   readonly attribute SVGPoint currentTranslate;
 
@@ -70,6 +71,7 @@ interface SVGSVGElement : SVGGraphicsElement {
   SVGTransform createSVGTransform();
   [NewObject]
   SVGTransform createSVGTransformFromMatrix(SVGMatrix matrix);
+  [UseCounter]
   Element? getElementById(DOMString elementId);
 };
 

dom/webidl/Window.webidl

@@ -368,7 +368,7 @@ Window implements OnErrorEventHandlerForWindow;
 #ifdef HAVE_SIDEBAR
 // Mozilla extension
 partial interface Window {
-  [Replaceable, Throws]
+  [Replaceable, Throws, UseCounter]
   readonly attribute (External or WindowProxy) sidebar;
 };
 #endif

image/DynamicImage.cpp

@@ -337,5 +337,11 @@ DynamicImage::Unwrap()
   return self.forget();
 }
 
+void
+DynamicImage::PropagateUseCounters(nsIDocument*)
+{
+  // No use counters.
+}
+
 } // namespace image
 } // namespace mozilla

image/ImageWrapper.cpp

@@ -291,6 +291,12 @@ ImageWrapper::SetAnimationStartTime(const TimeStamp& aTime)
   mInnerImage->SetAnimationStartTime(aTime);
 }
 
+void
+ImageWrapper::PropagateUseCounters(nsIDocument* aParentDocument)
+{
+  mInnerImage->PropagateUseCounters(aParentDocument);
+}
+
 nsIntSize
 ImageWrapper::OptimalImageSizeForDest(const gfxSize& aDest,
                                       uint32_t aWhichFrame,

image/RasterImage.cpp

@@ -1663,6 +1663,12 @@ RasterImage::Unwrap()
   return self.forget();
 }
 
+void
+RasterImage::PropagateUseCounters(nsIDocument*)
+{
+  // No use counters.
+}
+
 IntSize
 RasterImage::OptimalImageSizeForDest(const gfxSize& aDest, uint32_t aWhichFrame,
                                      SamplingFilter aSamplingFilter, uint32_t aFlags)

image/VectorImage.cpp

@@ -34,6 +34,7 @@
 #include "SVGDocumentWrapper.h"
 #include "nsIDOMEventListener.h"
 #include "SurfaceCache.h"
+#include "nsDocument.h"
 
 // undef the GetCurrentTime macro defined in WinBase.h from the MS Platform SDK
 #undef GetCurrentTime
@@ -1327,6 +1328,15 @@ VectorImage::InvalidateObserversOnNextRefreshDriverTick()
   }
 }
 
+void
+VectorImage::PropagateUseCounters(nsIDocument* aParentDocument)
+{
+  nsIDocument* doc = mSVGDocumentWrapper->GetDocument();
+  if (doc) {
+    doc->PropagateUseCounters(aParentDocument);
+  }
+}
+
 nsIntSize
 VectorImage::OptimalImageSizeForDest(const gfxSize& aDest,
                                      uint32_t aWhichFrame,

image/imgIContainer.idl

@@ -19,6 +19,8 @@
 #include "nsSize.h"
 #include "limits.h"
 
+class nsIDocument;
+
 namespace mozilla {
 namespace layers {
 class LayerManager;
@@ -65,6 +67,7 @@ native Orientation(mozilla::image::Orientation);
 native TempRefSourceSurface(already_AddRefed<mozilla::gfx::SourceSurface>);
 native TempRefImgIContainer(already_AddRefed<imgIContainer>);
 native nsIntSizeByVal(nsIntSize);
+[ptr] native nsIDocument(nsIDocument);
 
 
 /**
@@ -74,7 +77,7 @@ native nsIntSizeByVal(nsIntSize);
  *
  * Internally, imgIContainer also manages animation of images.
  */
-[scriptable, builtinclass, uuid(7ba72242-28da-4c5f-b53f-54da8874775e)]
+[scriptable, builtinclass, uuid(a8dbee24-ff86-4755-b40e-51175caf31af)]
 interface imgIContainer : nsISupports
 {
   /**
@@ -539,4 +542,10 @@ interface imgIContainer : nsISupports
    * Removes any ImageWrappers and returns the unwrapped base image.
    */
   [notxpcom, nostdcall] TempRefImgIContainer unwrap();
+
+  /*
+   * Propagate the use counters (if any) from this container to the passed in
+   * document.
+   */
+  [noscript, notxpcom] void propagateUseCounters(in nsIDocument aDocument);
 };

layout/generic/nsBulletFrame.cpp

@@ -775,6 +775,16 @@ nsBulletFrame::Notify(imgIRequest *aRequest, int32_t aType, const nsIntRect* aDa
     InvalidateFrame();
   }
 
+  if (aType == imgINotificationObserver::DECODE_COMPLETE) {
+    if (nsIDocument* parent = GetOurCurrentDoc()) {
+      nsCOMPtr<imgIContainer> container;
+      aRequest->GetImage(getter_AddRefs(container));
+      if (container) {
+        container->PropagateUseCounters(parent);
+      }
+    }
+  }
+
   return NS_OK;
 }
 

layout/style/ImageLoader.cpp

@@ -15,6 +15,7 @@
 #include "FrameLayerBuilder.h"
 #include "nsSVGEffects.h"
 #include "imgIContainer.h"
+#include "Image.h"
 
 namespace mozilla {
 namespace css {
@@ -394,6 +395,14 @@ ImageLoader::Notify(imgIRequest* aRequest, int32_t aType, const nsIntRect* aData
     return OnFrameUpdate(aRequest);
   }
 
+  if (aType == imgINotificationObserver::DECODE_COMPLETE) {
+    nsCOMPtr<imgIContainer> image;
+    aRequest->GetImage(getter_AddRefs(image));
+    if (image && mDocument) {
+      image->PropagateUseCounters(mDocument);
+    }
+  }
+
   return NS_OK;
 }
 
@@ -499,5 +508,19 @@ ImageLoader::UnblockOnload(imgIRequest* aRequest)
   return NS_OK;
 }
 
+void
+ImageLoader::FlushUseCounters()
+{
+  for (auto iter = mImages.Iter(); !iter.Done(); iter.Next()) {
+    nsPtrHashKey<Image>* key = iter.Get();
+    ImageLoader::Image* image = key->GetKey();
+
+    imgIRequest* request = image->mRequests.GetWeak(mDocument);
+
+    nsCOMPtr<imgIContainer> container;
+    request->GetImage(getter_AddRefs(container));
+  }
+}
+
 } // namespace css
 } // namespace mozilla

layout/style/ImageLoader.h

@@ -70,6 +70,8 @@ public:
 
   void DestroyRequest(imgIRequest* aRequest);
 
+  void FlushUseCounters();
+
 private:
   ~ImageLoader() {}
 

layout/style/nsCSSDataBlock.cpp

@@ -681,12 +681,14 @@ nsCSSExpandedDataBlock::TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
                                           bool aIsImportant,
                                           bool aOverrideImportant,
                                           bool aMustCallValueAppended,
-                                          css::Declaration* aDeclaration)
+                                          css::Declaration* aDeclaration,
+                                          nsIDocument* aSheetDocument)
 {
   if (!nsCSSProps::IsShorthand(aPropID)) {
     return DoTransferFromBlock(aFromBlock, aPropID,
                                aIsImportant, aOverrideImportant,
-                               aMustCallValueAppended, aDeclaration);
+                               aMustCallValueAppended, aDeclaration,
+                               aSheetDocument);
   }
 
   // We can pass CSSEnabledState::eIgnore (here, and in ClearProperty
@@ -698,7 +700,8 @@ nsCSSExpandedDataBlock::TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
   CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(p, aPropID, aEnabledState) {
     changed |= DoTransferFromBlock(aFromBlock, *p,
                                    aIsImportant, aOverrideImportant,
-                                   aMustCallValueAppended, aDeclaration);
+                                   aMustCallValueAppended, aDeclaration,
+                                   aSheetDocument);
   }
   return changed;
 }
@@ -709,7 +712,8 @@ nsCSSExpandedDataBlock::DoTransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
                                             bool aIsImportant,
                                             bool aOverrideImportant,
                                             bool aMustCallValueAppended,
-                                            css::Declaration* aDeclaration)
+                                            css::Declaration* aDeclaration,
+                                            nsIDocument* aSheetDocument)
 {
   bool changed = false;
   MOZ_ASSERT(aFromBlock.HasPropertyBit(aPropID), "oops");
@@ -737,6 +741,13 @@ nsCSSExpandedDataBlock::DoTransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
     aDeclaration->ValueAppended(aPropID);
   }
 
+  if (aSheetDocument) {
+    UseCounter useCounter = nsCSSProps::UseCounterFor(aPropID);
+    if (useCounter != eUseCounter_UNKNOWN) {
+      aSheetDocument->SetDocumentAndPageUseCounter(useCounter);
+    }
+  }
+
   SetPropertyBit(aPropID);
   aFromBlock.ClearPropertyBit(aPropID);
 

layout/style/nsCSSDataBlock.h

@@ -20,6 +20,7 @@
 
 struct nsRuleData;
 class nsCSSExpandedDataBlock;
+class nsIDocument;
 
 namespace mozilla {
 namespace css {
@@ -257,6 +258,8 @@ public:
    * Returns true if something changed, false otherwise.  Calls
    * |ValueAppended| on |aDeclaration| if the property was not
    * previously set, or in any case if |aMustCallValueAppended| is true.
+   * Calls |SetDocumentAndPageUseCounter| on |aSheetDocument| if it is
+   * non-null and |aPropID| has a use counter.
    */
   bool TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
                          nsCSSPropertyID aPropID,
@@ -264,7 +267,8 @@ public:
                          bool aIsImportant,
                          bool aOverrideImportant,
                          bool aMustCallValueAppended,
-                         mozilla::css::Declaration* aDeclaration);
+                         mozilla::css::Declaration* aDeclaration,
+                         nsIDocument* aSheetDocument);
 
   /**
    * Copies the values for aPropID into the specified aRuleData object.
@@ -298,7 +302,8 @@ private:
                              bool aIsImportant,
                              bool aOverrideImportant,
                              bool aMustCallValueAppended,
-                             mozilla::css::Declaration* aDeclaration);
+                             mozilla::css::Declaration* aDeclaration,
+                             nsIDocument* aSheetDocument);
 
 #ifdef DEBUG
   void DoAssertInitialState();

layout/style/nsCSSParser.cpp

@@ -143,6 +143,8 @@ public:
 
   nsresult SetStyleSheet(CSSStyleSheet* aSheet);
 
+  nsIDocument* GetDocument();
+
   nsresult SetQuirkMode(bool aQuirkMode);
 
   nsresult SetChildLoader(mozilla::css::Loader* aChildLoader);
@@ -1657,6 +1659,15 @@ CSSParserImpl::SetStyleSheet(CSSStyleSheet* aSheet)
   return NS_OK;
 }
 
+nsIDocument*
+CSSParserImpl::GetDocument()
+{
+  if (!mSheet) {
+    return nullptr;
+  }
+  return mSheet->GetDocument();
+}
+
 nsresult
 CSSParserImpl::SetQuirkMode(bool aQuirkMode)
 {
@@ -1978,7 +1989,8 @@ CSSParserImpl::ParseTransformProperty(const nsAString& aPropValue,
     declaration->ExpandTo(&mData);
     changed = mData.TransferFromBlock(mTempData, eCSSProperty_transform,
                                       EnabledState(), false,
-                                      true, false, declaration);
+                                      true, false, declaration,
+                                      GetDocument());
     declaration->CompressFrom(&mData);
   }
 
@@ -2059,7 +2071,8 @@ CSSParserImpl::ParseProperty(const nsCSSPropertyID aPropID,
       aDeclaration->ExpandTo(&mData);
       *aChanged = mData.TransferFromBlock(mTempData, aPropID,
                                           EnabledState(), aIsImportant,
-                                          true, false, aDeclaration);
+                                          true, false, aDeclaration,
+                                          GetDocument());
       aDeclaration->CompressFrom(&mData);
     }
     CLEAR_ERROR();
@@ -7573,7 +7586,7 @@ CSSParserImpl::ParseDeclaration(css::Declaration* aDeclaration,
     *aChanged |= mData.TransferFromBlock(mTempData, propID, EnabledState(),
                                          status == ePriority_Important,
                                          false, aMustCallValueAppended,
-                                         aDeclaration);
+                                         aDeclaration, GetDocument());
   }
 
   return true;
@@ -15355,17 +15368,17 @@ CSSParserImpl::ParseFontFeatureSettings(nsCSSValue& aValue)
   return true;
 }
 
-bool
-CSSParserImpl::ParseFontVariationSettings(nsCSSValue& aValue)
-{
-  // TODO: Actually implement this.
-  
-  // This stub is here because websites insist on considering this
-  // very hardware-dependent and O.S.-variable low-level font-control
-  // as a "critical feature" which it isn't as there is 0 guarantee
-  // that font variation settings are supported or honored by any
-  // operating system used by the client.
-  return true;
+bool
+CSSParserImpl::ParseFontVariationSettings(nsCSSValue& aValue)
+{
+  // TODO: Actually implement this.
+  
+  // This stub is here because websites insist on considering this
+  // very hardware-dependent and O.S.-variable low-level font-control
+  // as a "critical feature" which it isn't as there is 0 guarantee
+  // that font variation settings are supported or honored by any
+  // operating system used by the client.
+  return true;
 }
 
 bool

layout/style/nsCSSProps.cpp

@@ -3423,6 +3423,21 @@ nsCSSProps::gPropertyEnabled[eCSSProperty_COUNT_with_aliases] = {
   #undef IS_ENABLED_BY_DEFAULT
 };
 
+#include "../../dom/base/PropertyUseCounterMap.inc"
+
+/* static */ const UseCounter
+nsCSSProps::gPropertyUseCounter[eCSSProperty_COUNT_no_shorthands] = {
+  #define CSS_PROP_PUBLIC_OR_PRIVATE(publicname_, privatename_) privatename_
+  #define CSS_PROP_LIST_INCLUDE_LOGICAL
+  #define CSS_PROP(name_, id_, method_, flags_, pref_, parsevariant_,     \
+                   kwtable_, stylestruct_, stylestructoffset_, animtype_) \
+    static_cast<UseCounter>(USE_COUNTER_FOR_CSS_PROPERTY_##method_),
+  #include "nsCSSPropList.h"
+  #undef CSS_PROP
+  #undef CSS_PROP_LIST_INCLUDE_LOGICAL
+  #undef CSS_PROP_PUBLIC_OR_PRIVATE
+};
+
 // Check that all logical property flags are used appropriately.
 #define CSS_PROP(name_, id_, method_, flags_, pref_, parsevariant_,         \
                  kwtable_, stylestruct_, stylestructoffset_, animtype_)     \

layout/style/nsCSSProps.h

@@ -19,6 +19,7 @@
 #include "nsStyleStructFwd.h"
 #include "nsCSSKeywords.h"
 #include "mozilla/CSSEnabledState.h"
+#include "mozilla/UseCounter.h"
 #include "mozilla/EnumTypeTraits.h"
 
 // Length of the "--" prefix on custom names (such as custom property names,
@@ -639,8 +640,19 @@ public:
     return gPropertyEnabled[aProperty];
   }
 
+  // A table for the use counter associated with each CSS property.  If a
+  // property does not have a use counter defined in UseCounters.conf, then
+  // its associated entry is |eUseCounter_UNKNOWN|.
+  static const mozilla::UseCounter gPropertyUseCounter[eCSSProperty_COUNT_no_shorthands];
+
 public:
 
+  static mozilla::UseCounter UseCounterFor(nsCSSPropertyID aProperty) {
+    MOZ_ASSERT(0 <= aProperty && aProperty < eCSSProperty_COUNT_no_shorthands,
+               "out of range");
+    return gPropertyUseCounter[aProperty];
+  }
+
   static bool IsEnabled(nsCSSPropertyID aProperty, EnabledState aEnabled)
   {
     if (IsEnabled(aProperty)) {