Issue #618 - (async, preload) Correctly pass info about async/defer to parser.

This makes sure we don't block body-referred sub-resources by head-referenced
defer and async scripts. This is important for all script loads, not just
modules, but is added here because it was run into while implementing modules.

dom/script/ScriptLoader.cpp

@@ -1050,15 +1050,17 @@ ScriptLoader::StartLoad(ScriptLoadRequest *aRequest, const nsAString &aType,
   NS_ENSURE_SUCCESS(rv, rv);
 
   nsIScriptElement *script = aRequest->mElement;
+  bool async = script ? script->GetScriptAsync() : aRequest->mPreloadAsAsync;
+  bool defer = script ? script->GetScriptDeferred() : aRequest->mPreloadAsDefer;
+
   nsCOMPtr<nsIClassOfService> cos(do_QueryInterface(channel));
 
   if (cos) {
-    if (aScriptFromHead &&
+    if (aScriptFromHead && !async && !defer) {
-        !(script && (script->GetScriptAsync() || script->GetScriptDeferred()))) {
       // synchronous head scripts block lading of most other non js/css
       // content such as images
       cos->AddClassFlags(nsIClassOfService::Leader);
-    } else if (!(script && script->GetScriptDeferred())) {
+    } else if (!defer) {
       // other scripts are neither blocked nor prioritized unless marked deferred
       cos->AddClassFlags(nsIClassOfService::Unblocked);
     }
@@ -2571,6 +2573,8 @@ ScriptLoader::PreloadURI(nsIURI *aURI, const nsAString &aCharset,
                          const nsAString &aCrossOrigin,
                          const nsAString& aIntegrity,
                          bool aScriptFromHead,
+                         bool aAsync,
+                         bool aDefer,
                          const mozilla::net::ReferrerPolicy aReferrerPolicy)
 {
   NS_ENSURE_TRUE_VOID(mDocument);
@@ -2601,6 +2605,8 @@ ScriptLoader::PreloadURI(nsIURI *aURI, const nsAString &aCharset,
                       Element::StringToCORSMode(aCrossOrigin), sriMetadata,
                       aReferrerPolicy);
   request->mIsInline = false;
+  request->mPreloadAsAsync = aAsync;
+  request->mPreloadAsDefer = aDefer;
 
   nsresult rv = StartLoad(request, aType, aScriptFromHead);
   if (NS_FAILED(rv)) {

dom/script/ScriptLoader.h

@@ -76,6 +76,8 @@ public:
       mHasSourceMapURL(false),
       mInDeferList(false),
       mInAsyncList(false),
+      mPreloadAsAsync(false),
+      mPreloadAsDefer(false),
       mIsNonAsyncScriptInserted(false),
       mIsXSLT(false),
       mIsCanceled(false),
@@ -161,6 +163,8 @@ public:
   bool mHasSourceMapURL;  // Does the HTTP header have a source map url?
   bool mInDeferList;      // True if we live in mDeferRequests.
   bool mInAsyncList;      // True if we live in mLoadingAsyncRequests or mLoadedAsyncRequests.
+  bool mPreloadAsAsync;   // True if this is a preload request and the script is async
+  bool mPreloadAsDefer;   // True if this is a preload request and the script is defer
   bool mIsNonAsyncScriptInserted; // True if we live in mNonAsyncExternalScriptInsertedRequests
   bool mIsXSLT;           // True if we live in mXSLTRequests.
   bool mIsCanceled;       // True if we have been explicitly canceled.
@@ -459,6 +463,8 @@ public:
                           const nsAString &aCrossOrigin,
                           const nsAString& aIntegrity,
                           bool aScriptFromHead,
+                          bool aAsync,
+                          bool aDefer,
                           const mozilla::net::ReferrerPolicy aReferrerPolicy);
 
   /**

parser/html/nsHtml5SpeculativeLoad.cpp

@@ -6,9 +6,12 @@
 #include "nsHtml5TreeOpExecutor.h"
 
 nsHtml5SpeculativeLoad::nsHtml5SpeculativeLoad()
+ :
 #ifdef DEBUG
- : mOpCode(eSpeculativeLoadUninitialized)
+  mOpCode(eSpeculativeLoadUninitialized),
 #endif
+  mIsAsync(false),
+  mIsDefer(false)
 {
   MOZ_COUNT_CTOR(nsHtml5SpeculativeLoad);
 }
@@ -48,11 +51,13 @@ nsHtml5SpeculativeLoad::Perform(nsHtml5TreeOpExecutor* aExecutor)
       break;
     case eSpeculativeLoadScript:
       aExecutor->PreloadScript(mUrl, mCharset, mTypeOrCharsetSourceOrDocumentMode,
-                               mCrossOrigin, mIntegrity, false);
+                               mCrossOrigin, mIntegrity, false,
+                               mIsAsync, mIsDefer);
       break;
     case eSpeculativeLoadScriptFromHead:
       aExecutor->PreloadScript(mUrl, mCharset, mTypeOrCharsetSourceOrDocumentMode,
-                               mCrossOrigin, mIntegrity, true);
+                               mCrossOrigin, mIntegrity, true,
+                               mIsAsync, mIsDefer);
       break;
     case eSpeculativeLoadStyle:
       aExecutor->PreloadStyle(mUrl, mCharset, mCrossOrigin, mIntegrity);

parser/html/nsHtml5SpeculativeLoad.h

@@ -128,7 +128,9 @@ class nsHtml5SpeculativeLoad {
                            nsHtml5String aType,
                            nsHtml5String aCrossOrigin,
                            nsHtml5String aIntegrity,
-                           bool aParserInHead)
+                           bool aParserInHead,
+                           bool aAsync,
+                           bool aDefer)
     {
       NS_PRECONDITION(mOpCode == eSpeculativeLoadUninitialized,
                       "Trying to reinitialize a speculative load!");
@@ -139,6 +141,8 @@ class nsHtml5SpeculativeLoad {
       aType.ToString(mTypeOrCharsetSourceOrDocumentMode);
       aCrossOrigin.ToString(mCrossOrigin);
       aIntegrity.ToString(mIntegrity);
+      mIsAsync = aAsync;
+      mIsDefer = aDefer;
     }
 
     inline void InitStyle(nsHtml5String aUrl,
@@ -221,6 +225,13 @@ class nsHtml5SpeculativeLoad {
 
   private:
     eHtml5SpeculativeLoad mOpCode;
+
+    /**
+     * Whether the refering element has async and/or defer attributes.
+     */
+    bool mIsAsync;
+    bool mIsDefer;
+
     nsString mUrl;
     nsString mReferrerPolicy;
     nsString mMetaCSP;

parser/html/nsHtml5TreeBuilderCppSupplement.h

@@ -185,16 +185,20 @@ nsHtml5TreeBuilder::createElement(int32_t aNamespace,
               aAttributes->getValue(nsHtml5AttributeName::ATTR_CROSSORIGIN);
             nsHtml5String integrity =
               aAttributes->getValue(nsHtml5AttributeName::ATTR_INTEGRITY);
+            bool async =
+              aAttributes->contains(nsHtml5AttributeName::ATTR_ASYNC);
+            bool defer =
+              aAttributes->contains(nsHtml5AttributeName::ATTR_DEFER);
             mSpeculativeLoadQueue.AppendElement()->InitScript(
               url,
               charset,
               type,
               crossOrigin,
               integrity,
-              mode == nsHtml5TreeBuilder::IN_HEAD);
+              mode == nsHtml5TreeBuilder::IN_HEAD,
-            mCurrentHtmlScriptIsAsyncOrDefer =
+              async,
-              aAttributes->contains(nsHtml5AttributeName::ATTR_ASYNC) ||
+              defer);
-              aAttributes->contains(nsHtml5AttributeName::ATTR_DEFER);
+            mCurrentHtmlScriptIsAsyncOrDefer = async || defer;
           }
         } else if (nsHtml5Atoms::link == aName) {
           nsHtml5String rel =
@@ -297,7 +301,9 @@ nsHtml5TreeBuilder::createElement(int32_t aNamespace,
               type,
               crossOrigin,
               integrity,
-              mode == nsHtml5TreeBuilder::IN_HEAD);
+              mode == nsHtml5TreeBuilder::IN_HEAD,
+              false /* async */, 
+              false /* defer */);
           }
         } else if (nsHtml5Atoms::style == aName) {
           nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();

parser/html/nsHtml5TreeOpExecutor.cpp

@@ -921,14 +921,16 @@ nsHtml5TreeOpExecutor::PreloadScript(const nsAString& aURL,
                                      const nsAString& aType,
                                      const nsAString& aCrossOrigin,
                                      const nsAString& aIntegrity,
-                                     bool aScriptFromHead)
+                                     bool aScriptFromHead,
+                                     bool aAsync,
+                                     bool aDefer)
 {
   nsCOMPtr<nsIURI> uri = ConvertIfNotPreloadedYet(aURL);
   if (!uri) {
     return;
   }
   mDocument->ScriptLoader()->PreloadURI(uri, aCharset, aType, aCrossOrigin,
-                                        aIntegrity, aScriptFromHead,
+                                        aIntegrity, aScriptFromHead, aAsync, aDefer,
                                         mSpeculationReferrerPolicy);
 }
 

parser/html/nsHtml5TreeOpExecutor.h

@@ -249,7 +249,9 @@ class nsHtml5TreeOpExecutor final : public nsHtml5DocumentBuilder,
                        const nsAString& aType,
                        const nsAString& aCrossOrigin,
                        const nsAString& aIntegrity,
-                       bool aScriptFromHead);
+                       bool aScriptFromHead,
+                       bool aAsync,
+                       bool aDefer);
 
     void PreloadStyle(const nsAString& aURL, const nsAString& aCharset,
                       const nsAString& aCrossOrigin,