Reland: Script streaming: Add an option to make the main thread block (wait for parsing)

Source/bindings/core/v8/ScriptStreamer.h

Index: Source/bindings/core/v8/ScriptStreamer.h
diff --git a/Source/bindings/core/v8/ScriptStreamer.h b/Source/bindings/core/v8/ScriptStreamer.h
index c61e1337c796281606fc7a327a178078222dd4d3..9341871b3b5074875d150b8a1aa2c09bcc6710eb 100644
--- a/Source/bindings/core/v8/ScriptStreamer.h
+++ b/Source/bindings/core/v8/ScriptStreamer.h
@@ -5,6 +5,7 @@
 #ifndef ScriptStreamer_h
 #define ScriptStreamer_h
 
+#include "bindings/core/v8/ScriptStreamingMode.h"
 #include "core/dom/PendingScript.h"
 #include "wtf/RefCounted.h"
 
@@ -82,7 +83,7 @@ public:
 
     // Called by ScriptStreamingTask when it has streamed all data to V8 and V8
     // has processed it.
-    void streamingComplete();
+    void streamingCompleteOnBackgroundThread();
 
     static void setSmallScriptThresholdForTesting(size_t threshold)
     {
@@ -96,10 +97,16 @@ private:
     // streamed. Non-const for testing.
     static size_t kSmallScriptThreshold;
 
-    ScriptStreamer(ScriptResource*, v8::ScriptCompiler::StreamedSource::Encoding, PendingScript::Type);
+    ScriptStreamer(ScriptResource*, v8::ScriptCompiler::StreamedSource::Encoding, PendingScript::Type, ScriptStreamingMode);
 
+    void streamingComplete();
     void notifyFinishedToClient();
 
+    bool shouldBlockMainThread() const
+    {
+        return m_scriptStreamingMode == ScriptStreamingModeAllPlusBlockParsingBlocking && m_scriptType == PendingScript::ParsingBlocking;
+    }
+
     static const char* startedStreamingHistogramName(PendingScript::Type);
 
     static bool startStreamingInternal(PendingScript&, Settings*, ScriptState*, PendingScript::Type);
@@ -118,12 +125,14 @@ private:
     ScriptResourceClient* m_client;
     WTF::OwnPtr<v8::ScriptCompiler::ScriptStreamingTask> m_task;
     bool m_loadingFinished; // Whether loading from the network is done.
-    bool m_parsingFinished; // Whether the V8 side processing is done.
+    // Whether the V8 side processing is done. Will be used by the main thread
+    // and the streamer thread; guarded by m_mutex.
+    bool m_parsingFinished;
     // Whether we have received enough data to start the streaming.
     bool m_haveEnoughDataForStreaming;
 
     // Whether the script source code should be retrieved from the Resource
-    // instead of the ScriptStreamer.
+    // instead of the ScriptStreamer; guarded by m_mutex.
     bool m_streamingSuppressed;
 
     // What kind of cached data V8 produces during streaming.
@@ -131,6 +140,18 @@ private:
 
     // For recording metrics for different types of scripts separately.
     PendingScript::Type m_scriptType;
+
+    // Streaming mode defines whether the main thread should block and wait for
+    // the parsing to complete after the load has finished. See
+    // ScriptStreamer::notifyFinished for more information.
+    ScriptStreamingMode m_scriptStreamingMode;
+    Mutex m_mutex;
+    ThreadCondition m_parsingFinishedCondition;
+    // Whether the main thread is currently waiting on the parser thread in
+    // notifyFinished(). This also defines which thread should do the cleanup of
+    // the parsing task: if the main thread is waiting, the main thread should
+    // do it, otherwise the parser thread should do it. Guarded by m_mutex.
+    bool m_mainThreadWaitingForParserThread;
 };
 
 } // namespace blink