Move MainThreadTaskRunner off Oilpan heap to simplify posting.

third_party/WebKit/Source/core/dom/MainThreadTaskRunner.h

Index: third_party/WebKit/Source/core/dom/MainThreadTaskRunner.h
diff --git a/third_party/WebKit/Source/core/dom/MainThreadTaskRunner.h b/third_party/WebKit/Source/core/dom/MainThreadTaskRunner.h
index efcc7dc33c4506361dfee89c1daf1cdb8454da7c..0bdd69f0088ff6ac54b83ddf0df64a961d5e41c7 100644
--- a/third_party/WebKit/Source/core/dom/MainThreadTaskRunner.h
+++ b/third_party/WebKit/Source/core/dom/MainThreadTaskRunner.h
@@ -35,16 +35,18 @@
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Vector.h"
+#include "wtf/WeakPtr.h"
 
 namespace blink {
 
 class ExecutionContext;
 class ExecutionContextTask;
 
-class CORE_EXPORT MainThreadTaskRunner final : public GarbageCollectedFinalized<MainThreadTaskRunner> {
+class CORE_EXPORT MainThreadTaskRunner final {
+    USING_FAST_MALLOC(MainThreadTaskRunner);
     WTF_MAKE_NONCOPYABLE(MainThreadTaskRunner);
 public:
-    static MainThreadTaskRunner* create(ExecutionContext*);
+    static PassOwnPtr<MainThreadTaskRunner> create(ExecutionContext*);
 
     ~MainThreadTaskRunner();
 
@@ -64,15 +66,18 @@ private:
 
     void postTaskInternal(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, bool isInspectorTask);
 
-    Member<ExecutionContext> m_context;
+    // Untraced back reference to the owner Document;
+    // this object has identical lifetime to it.
+    UntracedMember<ExecutionContext> m_context;
     Timer<MainThreadTaskRunner> m_pendingTasksTimer;
     Vector<OwnPtr<ExecutionContextTask>> m_pendingTasks;
     bool m_suspended;
+    WeakPtrFactory<MainThreadTaskRunner> m_weakFactory;
 };
 
-inline MainThreadTaskRunner* MainThreadTaskRunner::create(ExecutionContext* context)
+inline PassOwnPtr<MainThreadTaskRunner> MainThreadTaskRunner::create(ExecutionContext* context)
 {
-    return new MainThreadTaskRunner(context);
+    return adoptPtr(new MainThreadTaskRunner(context));
 }
 
 } // namespace blink