Oilpan: Move MainThreadTaskRunner into Oilpan heap.

Source/core/dom/MainThreadTaskRunner.h

Index: Source/core/dom/MainThreadTaskRunner.h
diff --git a/Source/core/dom/MainThreadTaskRunner.h b/Source/core/dom/MainThreadTaskRunner.h
index c3c9287cc01706ceca563ad8e312d6a97fdacde3..48e7324a5717353c19fd81a9a9bca5f8d5f73e4a 100644
--- a/Source/core/dom/MainThreadTaskRunner.h
+++ b/Source/core/dom/MainThreadTaskRunner.h
@@ -29,7 +29,7 @@
 
 #include "core/CoreExport.h"
 #include "platform/Timer.h"
-
+#include "platform/heap/Handle.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/OwnPtr.h"
@@ -42,15 +42,17 @@ namespace blink {
 class ExecutionContext;
 class ExecutionContextTask;
 
-class CORE_EXPORT MainThreadTaskRunner {
+class CORE_EXPORT MainThreadTaskRunner final : public NoBaseWillBeGarbageCollectedFinalized<MainThreadTaskRunner> {
     WTF_MAKE_NONCOPYABLE(MainThreadTaskRunner);
-    WTF_MAKE_FAST_ALLOCATED(MainThreadTaskRunner);
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(MainThreadTaskRunner);
 
 public:
-    static PassOwnPtr<MainThreadTaskRunner> create(ExecutionContext*);
+    static PassOwnPtrWillBeRawPtr<MainThreadTaskRunner> create(ExecutionContext*);
 
     ~MainThreadTaskRunner();
 
+    DECLARE_TRACE();
+
     void postTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>); // Executes the task on context's thread asynchronously.
     void postInspectorTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>);
     void perform(PassOwnPtr<ExecutionContextTask>, bool);
@@ -63,16 +65,16 @@ private:
 
     void pendingTasksTimerFired(Timer<MainThreadTaskRunner>*);
 
-    ExecutionContext* m_context;
+    RawPtrWillBeMember<ExecutionContext> m_context;
     WeakPtrFactory<MainThreadTaskRunner> m_weakFactory;

[sof, 2015/08/18 07:15:31]

Doesn't this need to be eagerly finalized?

[haraken, 2015/08/18 08:08:54]

I don't see any issue in not eagerly finalizing the MainThreadTaskRunner, but I
agree that it's nasty to let the MainThreadTask keep WeakPtr<MainThreadRunner>.
(i.e., it's nasty to have a WeakPtr to an on-heap object -- it should be a
WeakPersistent or WeakMember.)

Would it be better to add #if !ENABLE(OILPAN) to m_weakFactory and use a
WeakPersistent from MainThreadTask to the MainThreadTaskRunner? (Maybe does it
need to be CrossThreadWeakPersistent?)

[sof, 2015/08/18 13:54:45]

Could you explain your reasoning behind that assessment?

It is a problem to have this task runner be able to access m_context if
it(Document) has already been finalized. Which it might have been if this object
isn't eagerly finalized.

     Timer<MainThreadTaskRunner> m_pendingTasksTimer;
     Vector<OwnPtr<ExecutionContextTask>> m_pendingTasks;
     bool m_suspended;
 };
 
-inline PassOwnPtr<MainThreadTaskRunner> MainThreadTaskRunner::create(ExecutionContext* context)
+inline PassOwnPtrWillBeRawPtr<MainThreadTaskRunner> MainThreadTaskRunner::create(ExecutionContext* context)
 {
-    return adoptPtr(new MainThreadTaskRunner(context));
+    return adoptPtrWillBeNoop(new MainThreadTaskRunner(context));
 }
 
 } // namespace