Stream scripts to V8 as they load - Blink side.

Source/core/html/parser/HTMLScriptRunner.cpp

Index: Source/core/html/parser/HTMLScriptRunner.cpp
diff --git a/Source/core/html/parser/HTMLScriptRunner.cpp b/Source/core/html/parser/HTMLScriptRunner.cpp
index 4e1da540a73b334182b6a95a4fcf32e75c74037a..9056d84076e03d2afc51536c2913a2acc764e9da 100644
--- a/Source/core/html/parser/HTMLScriptRunner.cpp
+++ b/Source/core/html/parser/HTMLScriptRunner.cpp
@@ -109,6 +109,8 @@ bool HTMLScriptRunner::isPendingScriptReady(const PendingScript& script)
         return false;
     if (script.resource() && !script.resource()->isLoaded())

[haraken, 2014/09/10 05:57:52]

Not related to this CL, is it possible that script.resource() is 0 here?

If script.resource() is 0, isPendingScriptReady returns true, which sounds very
strange.

[marja, 2014/09/11 09:15:38]

Hmm, no idea.

         return false;
+    if (script.isStreaming())
+        return false;
     return true;
 }
 
@@ -167,6 +169,10 @@ void HTMLScriptRunner::executePendingScriptAndDispatchEvent(PendingScript& pendi
 
 void HTMLScriptRunner::notifyFinished(Resource* cachedResource)
 {
+    // For a parser-blocking script, this function should be called only when
+    // the streaming is complete.
+    ASSERT(!(m_parserBlockingScript.resource() == cachedResource
+        && m_parserBlockingScript.isStreaming()));
     m_host->notifyScriptLoaded(cachedResource);
 }
 
@@ -255,8 +261,11 @@ void HTMLScriptRunner::requestParsingBlockingScript(Element* element)
     // We only care about a load callback if resource is not already
     // in the cache. Callers will attempt to run the m_parserBlockingScript
     // if possible before returning control to the parser.
-    if (!m_parserBlockingScriptAlreadyLoaded)
+    if (!m_parserBlockingScriptAlreadyLoaded) {
+        bool startedStreaming = ScriptStreamer::startStreaming(m_parserBlockingScript);
+        blink::Platform::current()->histogramEnumeration("WebCore.Scripts.ParsingBlocking.StartedStreaming", startedStreaming ? 1 : 0, 2);

[haraken, 2014/09/10 05:57:52]

You can add this in a separate CL.

[marja, 2014/09/11 09:15:38]

Hmm, which part? Calling startStreaming or the UMA? Why? I'll have a Finch
experiment for this, so even if I call startStreaming here, it'll only be
enabled for the finch population, not everybody. And the UMA is just one line,
so I don't see why I should create a separate CL for it.

         m_parserBlockingScript.watchForLoad(this);
+    }
 }
 
 void HTMLScriptRunner::requestDeferredScript(Element* element)
@@ -314,6 +323,8 @@ void HTMLScriptRunner::runScript(Element* script, const TextPosition& scriptStar
             return;
 
         if (scriptLoader->willExecuteWhenDocumentFinishedParsing()) {
+            // FIXME: in addition to parser blocking scripts, stream also
+            // scripts which are not parser blocking.
             requestDeferredScript(script);
         } else if (scriptLoader->readyToBeParserExecuted()) {
             if (m_scriptNestingLevel == 1) {