Create & use microtask work queue

Source/bindings/v8/V8PerIsolateData.h

Index: Source/bindings/v8/V8PerIsolateData.h
diff --git a/Source/bindings/v8/V8PerIsolateData.h b/Source/bindings/v8/V8PerIsolateData.h
index 28dcd09b7f85cc4a91dbac6fc0f4f12257a0bcd6..bedade85847d99be8c3d5897ab2ba7ca99e82a6b 100644
--- a/Source/bindings/v8/V8PerIsolateData.h
+++ b/Source/bindings/v8/V8PerIsolateData.h
@@ -104,6 +104,9 @@ public:
     int incrementRecursionLevel() { return ++m_recursionLevel; }
     int decrementRecursionLevel() { return --m_recursionLevel; }
 
+    bool performingMicrotaskCheckpoint() const { return m_performingMicrotaskCheckpoint; }
+    void setPerformingMicrotaskCheckpoint(bool performingMicrotaskCheckpoint) { m_performingMicrotaskCheckpoint = performingMicrotaskCheckpoint; }
+
 #ifndef NDEBUG
     int internalScriptRecursionLevel() const { return m_internalScriptRecursionLevel; }
     int incrementInternalScriptRecursionLevel() { return ++m_internalScriptRecursionLevel; }
@@ -163,6 +166,7 @@ private:
 #endif
     OwnPtr<GCEventData> m_gcEventData;
     bool m_shouldCollectGarbageSoon;
+    bool m_performingMicrotaskCheckpoint;
 };
 
 } // namespace WebCore