diff --git a/dom/ipc/FilePickerParent.cpp b/dom/ipc/FilePickerParent.cpp
index 1438e374fe..0271890758 100644
--- a/dom/ipc/FilePickerParent.cpp
+++ b/dom/ipc/FilePickerParent.cpp
@@ -286,6 +286,7 @@ FilePickerParent::RecvOpen(const int16_t& aSelectedType,
     }
   }
 
+  MOZ_ASSERT(!mCallback);
   mCallback = new FilePickerShownCallback(this);
 
   mFilePicker->Open(mCallback);
diff --git a/dom/ipc/FilePickerParent.h b/dom/ipc/FilePickerParent.h
index 332007a715..7ab2f7dab1 100644
--- a/dom/ipc/FilePickerParent.h
+++ b/dom/ipc/FilePickerParent.h
@@ -69,7 +69,7 @@ class FilePickerParent : public PFilePickerParent
 
   private:
     virtual ~FilePickerShownCallback() {}
-    FilePickerParent* mFilePickerParent;
+    RefPtr<FilePickerParent> mFilePickerParent;
   };
 
  private:
@@ -78,7 +78,7 @@ class FilePickerParent : public PFilePickerParent
   // This runnable is used to do some I/O operation on a separate thread.
   class IORunnable : public Runnable
   {
-    FilePickerParent* mFilePickerParent;
+    RefPtr<FilePickerParent> mFilePickerParent;
     nsTArray<nsCOMPtr<nsIFile>> mFiles;
     nsTArray<BlobImplOrString> mResults;
     nsCOMPtr<nsIEventTarget> mEventTarget;
diff --git a/dom/notification/Notification.cpp b/dom/notification/Notification.cpp
index 9a7c833794..5439a4fe59 100644
--- a/dom/notification/Notification.cpp
+++ b/dom/notification/Notification.cpp
@@ -1688,6 +1688,11 @@ Notification::GetPermissionInternal(nsISupports* aGlobal, ErrorResult& aRv)
   }
 
   nsCOMPtr<nsIPrincipal> principal = sop->GetPrincipal();
+  if (!principal) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return NotificationPermission::Denied;
+  }
+
   return GetPermissionInternal(principal, aRv);
 }
 
diff --git a/gfx/gl/SharedSurfaceGL.cpp b/gfx/gl/SharedSurfaceGL.cpp
index adb4429ae8..2639d64afa 100644
--- a/gfx/gl/SharedSurfaceGL.cpp
+++ b/gfx/gl/SharedSurfaceGL.cpp
@@ -94,7 +94,8 @@ SharedSurface_Basic::~SharedSurface_Basic()
         mGL->fDeleteFramebuffers(1, &mFB);
 
     if (mOwnsTex)
-        mGL->fDeleteTextures(1, &mTex);
+        if (mTex)
+            mGL->fDeleteTextures(1, &mTex);
 }
 
 
diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index cb249c254c..462edfd91e 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -7754,10 +7754,23 @@ bool
 BytecodeEmitter::emitLeftAssociative(ListNode* node)
 {
     // Left-associative operator chain.
-    if (!emitTree(node->head()))
-        return false;
     JSOp op = node->getOp();
-    ParseNode* nextExpr = node->head()->pn_next;
+    ParseNode* headExpr = node->head();
+    if (op == JSOP_IN && headExpr->isKind(PNK_NAME) && headExpr->as<NameNode>().isPrivateName()) {
+        // {Goanna} The only way a "naked" private name can show up as the leftmost side of an in-chain
+        //          is from an ergonomic brand check (`this.#x in ...` would be a PNK_DOT child node).
+        //          Instead of going through the emitTree machinery, we pretend that this identifier
+        //          reference is actually a string, which allows us to use the JSOP_IN interpreter routines.
+        //          This erroneously doesn't call updateLineNumberNotes, but this is not a big issue:
+        //          the begin pos is correct as we're on the start of the current tree, the end is on the
+        //          same line anyway.
+        if (!emitAtomOp(headExpr->as<NameNode>().atom(), JSOP_STRING))
+            return false;
+    } else {
+        if (!emitTree(headExpr))
+            return false;
+    }
+    ParseNode* nextExpr = headExpr->pn_next;
     do {
         if (!emitTree(nextExpr))
             return false;
diff --git a/js/src/frontend/FullParseHandler.h b/js/src/frontend/FullParseHandler.h
index e27b9f540a..d2c8bbc2df 100644
--- a/js/src/frontend/FullParseHandler.h
+++ b/js/src/frontend/FullParseHandler.h
@@ -965,6 +965,10 @@ FOR_EACH_PARSENODE_SUBCLASS(DECLARE_AS)
         return node->isKind(PNK_NAME);
     }
 
+    bool isPrivateName(Node node) {
+        return node->isKind(PNK_NAME) && node->as<NameNode>().isPrivateName();
+    }
+
     bool isArgumentsAnyParentheses(Node node, ExclusiveContext* cx) {
         return node->isKind(PNK_NAME) && node->as<NameNode>().atom() == cx->names().arguments;
     }
diff --git a/js/src/frontend/ParseNode.h b/js/src/frontend/ParseNode.h
index b1fcab0735..439a6d8937 100644
--- a/js/src/frontend/ParseNode.h
+++ b/js/src/frontend/ParseNode.h
@@ -953,6 +953,10 @@ class NameNode : public ParseNode
     JSAtom* atom() const {
         return pn_u.name.atom;
     }
+    
+    bool isPrivateName() const {
+        return atom()->asPropertyName()->latin1OrTwoByteChar(0) == '#';
+    }
 
     ParseNode* initializer() const {
         return pn_u.name.initOrStmt;
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 2f2d95cca8..7bbfdca926 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -8951,6 +8951,15 @@ Parser<ParseHandler>::orExpr1(InHandling inHandling, YieldHandling yieldHandling
         if (!tokenStream.getToken(&tok))
             return null();
 
+        // Ensure that if we have a private name lhs we are legally constructing a
+        // `#x in obj` expression:
+        if (handler.isPrivateName(pn)) {
+            if (tok != TOK_IN) {
+                error(JSMSG_ILLEGAL_PRIVATE_NAME);
+                return null();
+            }
+        }
+
         ParseNodeKind pnk;
         if (tok == TOK_IN ? inHandling == InAllowed : TokenKindIsBinaryOp(tok)) {
             // We're definitely not in a destructuring context, so report any
@@ -8987,7 +8996,20 @@ Parser<ParseHandler>::orExpr1(InHandling inHandling, YieldHandling yieldHandling
                 // If we have not detected a mixing error at this point, record that
                 // we have an unparenthesized expression, in case we have one later.
                 unparenthesizedExpression = EnforcedParentheses::CoalesceExpr;
-                break;                
+                break;
+              case TOK_IN:
+                // if the LHS is a private name, and the operator is In,
+                // ensure we're construcing an ergonomic brand check of
+                // '#x in y', rather than having a higher precedence operator
+                // like + cause a different reduction, such as
+                // 1 + #x in y.
+                if (handler.isPrivateName(pn)) {
+                    if (depth > 0 && Precedence(kindStack[depth - 1]) >= Precedence(PNK_IN)) {
+                        error(JSMSG_ILLEGAL_PRIVATE_NAME);
+                        return null();
+                    }
+                }
+                break;
               default:
                 // Do nothing in other cases.
                 break;
diff --git a/js/src/frontend/SyntaxParseHandler.h b/js/src/frontend/SyntaxParseHandler.h
index 818530cfe9..80ca13ce45 100644
--- a/js/src/frontend/SyntaxParseHandler.h
+++ b/js/src/frontend/SyntaxParseHandler.h
@@ -104,6 +104,9 @@ class SyntaxParseHandler
         // Node representing the "async" name, which may actually be a
         // contextual keyword.
         NodePotentialAsyncKeyword,
+        
+        // Node representing a private name. Handled mostly like NodeUnparenthesizedName. 
+        NodePrivateName,
 
         // Valuable for recognizing potential destructuring patterns.
         NodeUnparenthesizedArray,
@@ -212,6 +215,8 @@ FOR_EACH_PARSENODE_SUBCLASS(DECLARE_AS)
             return NodePotentialAsyncKeyword;
         if (name == cx->names().eval)
             return NodeUnparenthesizedEvalName;
+        if (name->length() >= 1 && name->latin1OrTwoByteChar(0) == '#')
+            return NodePrivateName;
         return NodeUnparenthesizedName;
     }
 
@@ -614,7 +619,8 @@ FOR_EACH_PARSENODE_SUBCLASS(DECLARE_AS)
         return node == NodeUnparenthesizedArgumentsName ||
                node == NodeUnparenthesizedEvalName ||
                node == NodeUnparenthesizedName ||
-               node == NodePotentialAsyncKeyword;
+               node == NodePotentialAsyncKeyword ||
+               node == NodePrivateName;
     }
 
     bool isNameAnyParentheses(Node node) {
@@ -625,6 +631,10 @@ FOR_EACH_PARSENODE_SUBCLASS(DECLARE_AS)
                node == NodeParenthesizedName;
     }
 
+    bool isPrivateName(Node node) {
+        return node == NodePrivateName;
+    }
+
     bool isArgumentsAnyParentheses(Node node, ExclusiveContext* cx) {
         return node == NodeUnparenthesizedArgumentsName || node == NodeParenthesizedArgumentsName;
     }
diff --git a/js/src/js.msg b/js/src/js.msg
index 1cb571d189..340cfd6ad2 100644
--- a/js/src/js.msg
+++ b/js/src/js.msg
@@ -364,6 +364,7 @@ MSG_DEF(JSMSG_BAD_NEW_OPTIONAL,        0, JSEXN_SYNTAXERR, "new keyword cannot b
 MSG_DEF(JSMSG_BAD_OPTIONAL_TEMPLATE,   0, JSEXN_SYNTAXERR, "tagged template cannot be used with optional chain")
 MSG_DEF(JSMSG_ESCAPED_KEYWORD,         0, JSEXN_SYNTAXERR, "keywords must be written literally, without embedded escapes")
 MSG_DEF(JSMSG_FIELDS_NOT_SUPPORTED,    0, JSEXN_SYNTAXERR, "fields are not currently supported")
+MSG_DEF(JSMSG_ILLEGAL_PRIVATE_NAME,    0, JSEXN_SYNTAXERR, "private names aren't valid in this context")
 
 // asm.js
 MSG_DEF(JSMSG_USE_ASM_TYPE_FAIL,       1, JSEXN_TYPEERR, "asm.js type error: {0}")
diff --git a/layout/style/nsCSSPropList.h b/layout/style/nsCSSPropList.h
index fa4cd1beb9..0694817515 100644
--- a/layout/style/nsCSSPropList.h
+++ b/layout/style/nsCSSPropList.h
@@ -373,7 +373,7 @@ CSS_PROP_DISPLAY(
     AnimationDelay,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_TIME, // used by list parsing
     nullptr,
     CSS_PROP_NO_OFFSET,
@@ -384,7 +384,7 @@ CSS_PROP_DISPLAY(
     AnimationDirection,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_KEYWORD, // used by list parsing
     kAnimationDirectionKTable,
     CSS_PROP_NO_OFFSET,
@@ -395,7 +395,7 @@ CSS_PROP_DISPLAY(
     AnimationDuration,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_TIME | VARIANT_NONNEGATIVE_DIMENSION, // used by list parsing
     nullptr,
     CSS_PROP_NO_OFFSET,
@@ -406,7 +406,7 @@ CSS_PROP_DISPLAY(
     AnimationFillMode,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_KEYWORD, // used by list parsing
     kAnimationFillModeKTable,
     CSS_PROP_NO_OFFSET,
@@ -420,7 +420,7 @@ CSS_PROP_DISPLAY(
         // http://lists.w3.org/Archives/Public/www-style/2011Mar/0355.html
         CSS_PROPERTY_VALUE_NONNEGATIVE |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_KEYWORD | VARIANT_NUMBER, // used by list parsing
     kAnimationIterationCountKTable,
     CSS_PROP_NO_OFFSET,
@@ -431,7 +431,7 @@ CSS_PROP_DISPLAY(
     AnimationName,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     // FIXME: The spec should say something about 'inherit' and 'initial'
     // not being allowed.
     VARIANT_NONE | VARIANT_IDENTIFIER_NO_INHERIT, // used by list parsing
@@ -444,7 +444,7 @@ CSS_PROP_DISPLAY(
     AnimationPlayState,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_KEYWORD, // used by list parsing
     kAnimationPlayStateKTable,
     CSS_PROP_NO_OFFSET,
@@ -455,7 +455,7 @@ CSS_PROP_DISPLAY(
     AnimationTimingFunction,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.animation.enabled",
     VARIANT_KEYWORD | VARIANT_TIMING_FUNCTION, // used by list parsing
     kTransitionTimingFunctionKTable,
     CSS_PROP_NO_OFFSET,
@@ -4284,7 +4284,7 @@ CSS_PROP_DISPLAY(
     TransitionDelay,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.transition.enabled",
     VARIANT_TIME, // used by list parsing
     nullptr,
     CSS_PROP_NO_OFFSET,
@@ -4295,7 +4295,7 @@ CSS_PROP_DISPLAY(
     TransitionDuration,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.transition.enabled",
     VARIANT_TIME | VARIANT_NONNEGATIVE_DIMENSION, // used by list parsing
     nullptr,
     CSS_PROP_NO_OFFSET,
@@ -4306,7 +4306,7 @@ CSS_PROP_DISPLAY(
     TransitionProperty,
     CSS_PROPERTY_PARSE_FUNCTION |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.transition.enabled",
     VARIANT_IDENTIFIER | VARIANT_NONE | VARIANT_ALL, // used only in shorthand
     nullptr,
     CSS_PROP_NO_OFFSET,
@@ -4317,7 +4317,7 @@ CSS_PROP_DISPLAY(
     TransitionTimingFunction,
     CSS_PROPERTY_PARSE_VALUE_LIST |
         CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
-    "",
+    "layout.css.transition.enabled",
     VARIANT_KEYWORD | VARIANT_TIMING_FUNCTION, // used by list parsing
     kTransitionTimingFunctionKTable,
     CSS_PROP_NO_OFFSET,
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 742fde5568..6dd82c9bf5 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -2486,6 +2486,12 @@ pref("layout.css.mix-blend-mode.enabled", true);
 // Is support for isolation enabled?
 pref("layout.css.isolation.enabled", true);
 
+// Is support for CSS animation properties enabled?
+pref("layout.css.animation.enabled", true);
+
+// Is support for CSS transition properties enabled?
+pref("layout.css.transition.enabled", true);
+
 // Is support for CSS Filters enabled?
 pref("layout.css.filters.enabled", true);
 
diff --git a/netwerk/protocol/websocket/WebSocketChannel.cpp b/netwerk/protocol/websocket/WebSocketChannel.cpp
index 058dc46417..9fca09a087 100644
--- a/netwerk/protocol/websocket/WebSocketChannel.cpp
+++ b/netwerk/protocol/websocket/WebSocketChannel.cpp
@@ -520,7 +520,7 @@ private:
     ~nsOpenConn() { MOZ_COUNT_DTOR(nsOpenConn); }
 
     nsCString mAddress;
-    WebSocketChannel *mChannel;
+    RefPtr<WebSocketChannel> mChannel;
   };
 
   void ConnectNext(nsCString &hostName)
@@ -1191,6 +1191,7 @@ WebSocketChannel::WebSocketChannel() :
   mBufferSize(kIncomingBufferInitialSize),
   mCurrentOut(nullptr),
   mCurrentOutSent(0),
+  mCompressorMutex("WebSocketChannel::mCompressorMutex"),
   mDynamicOutputSize(0),
   mDynamicOutput(nullptr),
   mPrivateBrowsing(false),
@@ -1627,6 +1628,7 @@ WebSocketChannel::ProcessInput(uint8_t *buffer, uint32_t count)
     if (rsvBits) {
       // PMCE sets RSV1 bit in the first fragment when the non-control frame
       // is deflated
+      MutexAutoLock lock(mCompressorMutex);
       if (mPMCECompressor && rsvBits == kRsv1Bit && mFragmentAccumulator == 0 &&
           !(opcode & kControlFrameMask)) {
         mPMCECompressor->SetMessageDeflated();
@@ -1700,25 +1702,28 @@ WebSocketChannel::ProcessInput(uint8_t *buffer, uint32_t count)
       LOG(("WebSocketChannel:: ignoring read frame code %d after completion\n",
            opcode));
     } else if (opcode == nsIWebSocketFrame::OPCODE_TEXT) {
-      bool isDeflated = mPMCECompressor && mPMCECompressor->IsMessageDeflated();
-      LOG(("WebSocketChannel:: %stext frame received\n",
-           isDeflated ? "deflated " : ""));
-
       if (mListenerMT) {
         nsCString utf8Data;
 
-        if (isDeflated) {
-          rv = mPMCECompressor->Inflate(payload, payloadLength, utf8Data);
-          if (NS_FAILED(rv)) {
-            return rv;
-          }
-          LOG(("WebSocketChannel:: message successfully inflated "
-               "[origLength=%d, newLength=%d]\n", payloadLength,
-               utf8Data.Length()));
-        } else {
-          if (!utf8Data.Assign((const char *)payload, payloadLength,
-                               mozilla::fallible)) {
-            return NS_ERROR_OUT_OF_MEMORY;
+        { // lockscope
+          MutexAutoLock lock(mCompressorMutex);
+          bool isDeflated = mPMCECompressor && mPMCECompressor->IsMessageDeflated();
+          LOG(("WebSocketChannel:: %stext frame received\n",
+               isDeflated ? "deflated " : ""));
+
+          if (isDeflated) {
+            rv = mPMCECompressor->Inflate(payload, payloadLength, utf8Data);
+            if (NS_FAILED(rv)) {
+              return rv;
+            }
+            LOG(("WebSocketChannel:: message successfully inflated "
+                 "[origLength=%d, newLength=%d]\n", payloadLength,
+                 utf8Data.Length()));
+          } else {
+            if (!utf8Data.Assign((const char *)payload, payloadLength,
+                                 mozilla::fallible)) {
+              return NS_ERROR_OUT_OF_MEMORY;
+            }
           }
         }
 
@@ -1835,25 +1840,28 @@ WebSocketChannel::ProcessInput(uint8_t *buffer, uint32_t count)
         mService->FrameReceived(mSerial, mInnerWindowID, frame.forget());
       }
     } else if (opcode == nsIWebSocketFrame::OPCODE_BINARY) {
-      bool isDeflated = mPMCECompressor && mPMCECompressor->IsMessageDeflated();
-      LOG(("WebSocketChannel:: %sbinary frame received\n",
-           isDeflated ? "deflated " : ""));
-
       if (mListenerMT) {
         nsCString binaryData;
 
-        if (isDeflated) {
-          rv = mPMCECompressor->Inflate(payload, payloadLength, binaryData);
-          if (NS_FAILED(rv)) {
-            return rv;
-          }
-          LOG(("WebSocketChannel:: message successfully inflated "
-               "[origLength=%d, newLength=%d]\n", payloadLength,
-               binaryData.Length()));
-        } else {
-          if (!binaryData.Assign((const char *)payload, payloadLength,
-                                 mozilla::fallible)) {
-            return NS_ERROR_OUT_OF_MEMORY;
+        { //lockscope
+          MutexAutoLock lock(mCompressorMutex);
+          bool isDeflated = mPMCECompressor && mPMCECompressor->IsMessageDeflated();
+          LOG(("WebSocketChannel:: %sbinary frame received\n",
+               isDeflated ? "deflated " : ""));
+
+          if (isDeflated) {
+            rv = mPMCECompressor->Inflate(payload, payloadLength, binaryData);
+            if (NS_FAILED(rv)) {
+              return rv;
+            }
+            LOG(("WebSocketChannel:: message successfully inflated "
+                 "[origLength=%d, newLength=%d]\n", payloadLength,
+                 binaryData.Length()));
+          } else {
+            if (!binaryData.Assign((const char *)payload, payloadLength,
+                                   mozilla::fallible)) {
+              return NS_ERROR_OUT_OF_MEMORY;
+            }
           }
         }
 
@@ -2156,6 +2164,7 @@ WebSocketChannel::PrimeNewOutgoingMessage()
     }
 
     // deflate the payload if PMCE is negotiated
+    MutexAutoLock lock(mCompressorMutex);
     if (mPMCECompressor &&
         (msgType == kMsgTypeString || msgType == kMsgTypeBinaryString)) {
       if (mCurrentOut->DeflatePayload(mPMCECompressor)) {
@@ -2447,7 +2456,10 @@ WebSocketChannel::StopSession(nsresult reason)
     mCancelable = nullptr;
   }
 
-  mPMCECompressor = nullptr;
+  {
+    MutexAutoLock lock(mCompressorMutex);
+    mPMCECompressor = nullptr;
+  }
 
   if (!mCalledOnStop) {
     mCalledOnStop = 1;
@@ -2702,6 +2714,7 @@ WebSocketChannel::HandleExtensions()
     serverMaxWindowBits = 15;
   }
 
+  MutexAutoLock lock(mCompressorMutex);
   mPMCECompressor = new PMCECompression(clientNoContextTakeover,
                                         clientMaxWindowBits,
                                         serverMaxWindowBits);
@@ -3678,6 +3691,7 @@ WebSocketChannel::OnTransportAvailable(nsISocketTransport *aTransport,
         serverMaxWindowBits = 15;
       }
 
+      MutexAutoLock lock(mCompressorMutex);
       mPMCECompressor = new PMCECompression(serverNoContextTakeover,
                                             serverMaxWindowBits,
                                             clientMaxWindowBits);
diff --git a/netwerk/protocol/websocket/WebSocketChannel.h b/netwerk/protocol/websocket/WebSocketChannel.h
index bd75ca3a81..bd9717d529 100644
--- a/netwerk/protocol/websocket/WebSocketChannel.h
+++ b/netwerk/protocol/websocket/WebSocketChannel.h
@@ -18,6 +18,7 @@
 #include "nsIChannelEventSink.h"
 #include "nsIHttpChannelInternal.h"
 #include "nsIStringStream.h"
+#include "mozilla/Mutex.h"
 #include "BaseWebSocketChannel.h"
 
 #include "nsCOMPtr.h"
@@ -288,6 +289,7 @@ private:
   uint32_t                        mHdrOutToSend;
   uint8_t                        *mHdrOut;
   uint8_t                         mOutHeader[kCopyBreak + 16];
+  Mutex                           mCompressorMutex;
   nsAutoPtr<PMCECompression>      mPMCECompressor;
   uint32_t                        mDynamicOutputSize;
   uint8_t                        *mDynamicOutput;
diff --git a/python/mozbuild/mozbuild/backend/common.py b/python/mozbuild/mozbuild/backend/common.py
index 12b2a27c45..2e8a161815 100644
--- a/python/mozbuild/mozbuild/backend/common.py
+++ b/python/mozbuild/mozbuild/backend/common.py
@@ -29,6 +29,7 @@ from mozbuild.frontend.data import (
     FinalTargetFiles,
     GeneratedEventWebIDLFile,
     GeneratedWebIDLFile,
+    PreprocessedIPDLFile,
     PreprocessedTestWebIDLFile,
     PreprocessedWebIDLFile,
     SharedLibrary,
@@ -215,6 +216,21 @@ class BinariesCollection(object):
         self.shared_libraries = []
         self.programs = []
 
+class IPDLCollection(object):
+    """Collects IPDL files during the build."""
+
+    def __init__(self):
+        self.sources = set()
+        self.preprocessed_sources = set()
+
+    def all_sources(self):
+        return self.sources | self.preprocessed_sources
+
+    def all_regular_sources(self):
+        return self.sources
+
+    def all_preprocessed_sources(self):
+        return self.preprocessed_sources
 
 class CommonBackend(BuildBackend):
     """Holds logic common to all build backends."""
@@ -225,7 +241,7 @@ class CommonBackend(BuildBackend):
         self._webidls = WebIDLCollection()
         self._binaries = BinariesCollection()
         self._configs = set()
-        self._ipdl_sources = set()
+        self._ipdls = IPDLCollection()
 
     def consume_object(self, obj):
         self._configs.add(obj.config)
@@ -290,6 +306,10 @@ class CommonBackend(BuildBackend):
             self._webidls.generated_sources.add(mozpath.join(obj.srcdir,
                 obj.basename))
 
+        elif isinstance(obj, PreprocessedIPDLFile):
+            self._ipdls.preprocessed_sources.add(mozpath.join(
+                obj.srcdir, obj.basename))
+
         elif isinstance(obj, PreprocessedWebIDLFile):
             # WebIDL isn't relevant to artifact builds.
             if self.environment.is_artifact_build:
@@ -310,7 +330,7 @@ class CommonBackend(BuildBackend):
             if self.environment.is_artifact_build:
                 return True
 
-            self._ipdl_sources.add(mozpath.join(obj.srcdir, obj.basename))
+            self._ipdls.sources.add(mozpath.join(obj.srcdir, obj.basename))
 
         elif isinstance(obj, UnifiedSources):
             # Unified sources aren't relevant to artifact builds.
@@ -341,7 +361,9 @@ class CommonBackend(BuildBackend):
 
         self._handle_webidl_collection(self._webidls)
 
-        sorted_ipdl_sources = list(sorted(self._ipdl_sources))
+        sorted_ipdl_sources = list(sorted(self._ipdls.all_sources()))
+        sorted_nonstatic_ipdl_sources = list(sorted(self._ipdls.all_preprocessed_sources()))
+        sorted_static_ipdl_sources = list(sorted(self._ipdls.all_regular_sources()))
 
         def files_from(ipdl):
             base = mozpath.basename(ipdl)
@@ -364,7 +386,8 @@ class CommonBackend(BuildBackend):
                                                           files_per_unified_file=16))
 
         self._write_unified_files(unified_source_mapping, ipdl_dir, poison_windows_h=False)
-        self._handle_ipdl_sources(ipdl_dir, sorted_ipdl_sources, unified_source_mapping)
+        self._handle_ipdl_sources(ipdl_dir, sorted_ipdl_sources, sorted_nonstatic_ipdl_sources,
+                                  sorted_static_ipdl_sources, unified_source_mapping)
 
         for config in self._configs:
             self.backend_input_files.add(config.source)
diff --git a/python/mozbuild/mozbuild/backend/recursivemake.py b/python/mozbuild/mozbuild/backend/recursivemake.py
index a314124f44..5621bc7e92 100644
--- a/python/mozbuild/mozbuild/backend/recursivemake.py
+++ b/python/mozbuild/mozbuild/backend/recursivemake.py
@@ -1407,18 +1407,32 @@ class RecursiveMakeBackend(CommonBackend):
 
         self._makefile_out_count += 1
 
-    def _handle_ipdl_sources(self, ipdl_dir, sorted_ipdl_sources,
-                             unified_ipdl_cppsrcs_mapping):
+    def _handle_ipdl_sources(self, ipdl_dir, sorted_ipdl_sources, sorted_nonstatic_ipdl_sources,
+                             sorted_static_ipdl_sources, unified_ipdl_cppsrcs_mapping):
         # Write out a master list of all IPDL source files.
         mk = Makefile()
 
-        mk.add_statement('ALL_IPDLSRCS := %s' % ' '.join(sorted_ipdl_sources))
+        sorted_nonstatic_ipdl_basenames = list()
+        for source in sorted_nonstatic_ipdl_sources:
+            basename = os.path.basename(source)
+            sorted_nonstatic_ipdl_basenames.append(basename)
+            rule = mk.create_rule([basename])
+            rule.add_dependencies([source])
+            rule.add_commands([
+                '$(RM) $@',
+                '$(call py_action,preprocessor,$(DEFINES) $(ACDEFINES) '
+                    '$< -o $@)'
+            ])
+
+        mk.add_statement('ALL_IPDLSRCS := %s %s' % (' '.join(sorted_nonstatic_ipdl_basenames),
+                         ' '.join(sorted_static_ipdl_sources)))
 
         self._add_unified_build_rules(mk, unified_ipdl_cppsrcs_mapping,
                                       unified_files_makefile_variable='CPPSRCS')
 
-        mk.add_statement('IPDLDIRS := %s' % ' '.join(sorted(set(mozpath.dirname(p)
-            for p in self._ipdl_sources))))
+        # Preprocessed ipdl files are generated in ipdl_dir.
+        mk.add_statement('IPDLDIRS := %s %s' % (ipdl_dir, ' '.join(sorted(set(mozpath.dirname(p)
+            for p in sorted_static_ipdl_sources)))))
 
         with self._write_file(mozpath.join(ipdl_dir, 'ipdlsrcs.mk')) as ipdls:
             mk.dump(ipdls, removal_guard=False)
diff --git a/python/mozbuild/mozbuild/backend/tup.py b/python/mozbuild/mozbuild/backend/tup.py
index 0f7250eb01..b148532c89 100644
--- a/python/mozbuild/mozbuild/backend/tup.py
+++ b/python/mozbuild/mozbuild/backend/tup.py
@@ -298,8 +298,8 @@ class TupOnly(CommonBackend, PartialBackend):
             outputs=[output],
         )
 
-    def _handle_ipdl_sources(self, ipdl_dir, sorted_ipdl_sources,
-                             unified_ipdl_cppsrcs_mapping):
+    def _handle_ipdl_sources(self, ipdl_dir, sorted_ipdl_sources, sorted_nonstatic_ipdl_sources,
+                             sorted_static_ipdl_sources, unified_ipdl_cppsrcs_mapping):
         # TODO: This isn't implemented yet in the tup backend, but it is called
         # by the CommonBackend.
         pass
diff --git a/python/mozbuild/mozbuild/compilation/database.py b/python/mozbuild/mozbuild/compilation/database.py
index 4193e1bcf4..20b09df488 100644
--- a/python/mozbuild/mozbuild/compilation/database.py
+++ b/python/mozbuild/mozbuild/compilation/database.py
@@ -177,8 +177,8 @@ class CompileDBBackend(CommonBackend):
     def _handle_idl_manager(self, idl_manager):
         pass
 
-    def _handle_ipdl_sources(self, ipdl_dir, sorted_ipdl_sources,
-                             unified_ipdl_cppsrcs_mapping):
+    def _handle_ipdl_sources(self, ipdl_dir, sorted_ipdl_sources, sorted_nonstatic_ipdl_sources,
+                             sorted_static_ipdl_sources, unified_ipdl_cppsrcs_mapping):
         for f in unified_ipdl_cppsrcs_mapping:
             self._build_db_line(ipdl_dir, None, self.environment, f[0],
                                 '.cpp')
diff --git a/python/mozbuild/mozbuild/frontend/context.py b/python/mozbuild/mozbuild/frontend/context.py
index eb501dc666..ef9406ea5b 100644
--- a/python/mozbuild/mozbuild/frontend/context.py
+++ b/python/mozbuild/mozbuild/frontend/context.py
@@ -1441,6 +1441,13 @@ VARIABLES = {
         not use this flag.
         """),
 
+    'PREPROCESSED_IPDL_SOURCES': (StrictOrderingOnAppendList, list,
+        """Preprocessed IPDL source files.
+
+        These files will be preprocessed, then parsed and converted to
+        ``.cpp`` files.
+        """),
+
     'IPDL_SOURCES': (StrictOrderingOnAppendList, list,
         """IPDL source files.
 
diff --git a/python/mozbuild/mozbuild/frontend/data.py b/python/mozbuild/mozbuild/frontend/data.py
index fb0bf2405c..759469d233 100644
--- a/python/mozbuild/mozbuild/frontend/data.py
+++ b/python/mozbuild/mozbuild/frontend/data.py
@@ -218,6 +218,18 @@ class IPDLFile(ContextDerived):
 
         self.basename = path
 
+class PreprocessedIPDLFile(ContextDerived):
+    """Describes an individual .ipdl source file that requires preprocessing."""
+
+    __slots__ = (
+        'basename',
+    )
+
+    def __init__(self, context, path):
+        ContextDerived.__init__(self, context)
+
+        self.basename = path
+
 class WebIDLFile(ContextDerived):
     """Describes an individual .webidl source file."""
 
diff --git a/python/mozbuild/mozbuild/frontend/emitter.py b/python/mozbuild/mozbuild/frontend/emitter.py
index 25c5826626..6220cd4b4b 100644
--- a/python/mozbuild/mozbuild/frontend/emitter.py
+++ b/python/mozbuild/mozbuild/frontend/emitter.py
@@ -58,6 +58,7 @@ from .data import (
     ObjdirFiles,
     ObjdirPreprocessedFiles,
     PerSourceFlag,
+    PreprocessedIPDLFile,
     PreprocessedTestWebIDLFile,
     PreprocessedWebIDLFile,
     Program,
@@ -872,6 +873,7 @@ class TreeMetadataEmitter(LoggingMixin):
             ('GENERATED_EVENTS_WEBIDL_FILES', GeneratedEventWebIDLFile),
             ('GENERATED_WEBIDL_FILES', GeneratedWebIDLFile),
             ('IPDL_SOURCES', IPDLFile),
+            ('PREPROCESSED_IPDL_SOURCES', PreprocessedIPDLFile),
             ('PREPROCESSED_TEST_WEBIDL_FILES', PreprocessedTestWebIDLFile),
             ('PREPROCESSED_WEBIDL_FILES', PreprocessedWebIDLFile),
             ('TEST_WEBIDL_FILES', TestWebIDLFile),
diff --git a/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/bar/moz.build b/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/bar/moz.build
index eb37725230..126854c383 100644
--- a/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/bar/moz.build
+++ b/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/bar/moz.build
@@ -3,6 +3,10 @@
 # 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/.
 
+PREPROCESSED_IPDL_SOURCES += [
+    'bar1.ipdl',
+]
+
 IPDL_SOURCES += [
     'bar.ipdl',
     'bar2.ipdlh',
diff --git a/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/foo/moz.build b/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/foo/moz.build
index 84d40ac1d3..4047c31216 100644
--- a/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/foo/moz.build
+++ b/python/mozbuild/mozbuild/test/backend/data/ipdl_sources/foo/moz.build
@@ -3,6 +3,10 @@
 # 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/.
 
+PREPROCESSED_IPDL_SOURCES += [
+    'foo1.ipdl',
+]
+
 IPDL_SOURCES += [
     'foo.ipdl',
     'foo2.ipdlh',
diff --git a/python/mozbuild/mozbuild/test/backend/test_recursivemake.py b/python/mozbuild/mozbuild/test/backend/test_recursivemake.py
index 87f50f4973..a592ab55a3 100644
--- a/python/mozbuild/mozbuild/test/backend/test_recursivemake.py
+++ b/python/mozbuild/mozbuild/test/backend/test_recursivemake.py
@@ -656,7 +656,7 @@ class TestRecursiveMakeBackend(BackendTester):
             self.assertEqual(m, m2)
 
     def test_ipdl_sources(self):
-        """Test that IPDL_SOURCES are written to ipdlsrcs.mk correctly."""
+        """Test that PREPROCESSED_IPDL_SOURCES and IPDL_SOURCES are written to ipdlsrcs.mk correctly."""
         env = self._consume('ipdl_sources', RecursiveMakeBackend)
 
         manifest_path = mozpath.join(env.topobjdir,
@@ -667,9 +667,9 @@ class TestRecursiveMakeBackend(BackendTester):
         topsrcdir = env.topsrcdir.replace(os.sep, '/')
 
         expected = [
-            "ALL_IPDLSRCS := %s/bar/bar.ipdl %s/bar/bar2.ipdlh %s/foo/foo.ipdl %s/foo/foo2.ipdlh" % tuple([topsrcdir] * 4),
+            "ALL_IPDLSRCS := bar1.ipdl foo1.ipdl %s/bar/bar.ipdl %s/bar/bar2.ipdlh %s/foo/foo.ipdl %s/foo/foo2.ipdlh" % tuple([topsrcdir] * 4),
             "CPPSRCS := UnifiedProtocols0.cpp",
-            "IPDLDIRS := %s/bar %s/foo" % (topsrcdir, topsrcdir),
+            "IPDLDIRS := %s/ipc/ipdl %s/bar %s/foo" % (env.topobjdir, topsrcdir, topsrcdir),
         ]
 
         found = [str for str in lines if str.startswith(('ALL_IPDLSRCS',
diff --git a/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/bar/moz.build b/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/bar/moz.build
index eb37725230..126854c383 100644
--- a/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/bar/moz.build
+++ b/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/bar/moz.build
@@ -3,6 +3,10 @@
 # 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/.
 
+PREPROCESSED_IPDL_SOURCES += [
+    'bar1.ipdl',
+]
+
 IPDL_SOURCES += [
     'bar.ipdl',
     'bar2.ipdlh',
diff --git a/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/foo/moz.build b/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/foo/moz.build
index 84d40ac1d3..4047c31216 100644
--- a/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/foo/moz.build
+++ b/python/mozbuild/mozbuild/test/frontend/data/ipdl_sources/foo/moz.build
@@ -3,6 +3,10 @@
 # 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/.
 
+PREPROCESSED_IPDL_SOURCES += [
+    'foo1.ipdl',
+]
+
 IPDL_SOURCES += [
     'foo.ipdl',
     'foo2.ipdlh',
diff --git a/python/mozbuild/mozbuild/test/frontend/test_emitter.py b/python/mozbuild/mozbuild/test/frontend/test_emitter.py
index 191727381d..e1e3fa5ce2 100644
--- a/python/mozbuild/mozbuild/test/frontend/test_emitter.py
+++ b/python/mozbuild/mozbuild/test/frontend/test_emitter.py
@@ -30,6 +30,7 @@ from mozbuild.frontend.data import (
     JARManifest,
     LinkageMultipleRustLibrariesError,
     LocalInclude,
+    PreprocessedIPDLFile,
     Program,
     SdkFiles,
     SharedLibrary,
@@ -688,9 +689,12 @@ class TestEmitterBasic(unittest.TestCase):
         objs = self.read_topsrcdir(reader)
 
         ipdls = []
+        nonstatic_ipdls = []
         for o in objs:
             if isinstance(o, IPDLFile):
                 ipdls.append('%s/%s' % (o.relativedir, o.basename))
+            elif isinstance(o, PreprocessedIPDLFile):
+                nonstatic_ipdls.append('%s/%s' % (o.relativedir, o.basename))
 
         expected = [
             'bar/bar.ipdl',
@@ -699,7 +703,12 @@ class TestEmitterBasic(unittest.TestCase):
             'foo/foo2.ipdlh',
         ]
 
-        self.assertEqual(ipdls, expected)
+        expected = [
+            'bar/bar1.ipdl',
+            'foo/foo1.ipdl',
+        ]
+
+        self.assertEqual(nonstatic_ipdls, expected)
 
     def test_local_includes(self):
         """Test that LOCAL_INCLUDES is emitted correctly."""
diff --git a/xpcom/io/nsLocalFileWin.cpp b/xpcom/io/nsLocalFileWin.cpp
index 5182b71f6f..5210885dd9 100644
--- a/xpcom/io/nsLocalFileWin.cpp
+++ b/xpcom/io/nsLocalFileWin.cpp
@@ -3090,7 +3090,8 @@ nsLocalFile::IsExecutable(bool* aResult)
       "ws",
       "wsc",
       "wsf",
-      "wsh"
+      "wsh",
+      "xll"          // MS Excel dynamic link library
     };
     nsDependentSubstring ext = Substring(path, dotIdx + 1);
     for (size_t i = 0; i < ArrayLength(executableExts); ++i) {