Oilpan: disable conservative GCs during initial GC mixin construction.

Source/core/frame/DeviceSingleWindowEventController.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DeviceSingleWindowEventController_h
 #define DeviceSingleWindowEventController_h
 
 #include "core/frame/DOMWindowLifecycleObserver.h"
 #include "core/frame/PlatformEventController.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class Document;
 class Event;
 
 class DeviceSingleWindowEventController : public NoBaseWillBeGarbageCollectedFinalized<DeviceSingleWindowEventController>, public PlatformEventController, public DOMWindowLifecycleObserver {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(DeviceSingleWindowEventController);

[haraken, 2015/03/05 02:20:19]

Why can we remove this?

[sof, 2015/03/05 07:14:58]

It's an abstract class with all objects that implement it are also declared as
GC mixins. The declaration here serves no purpose?

(I can split the change out, its presence initially created some extra problems
for this CL.)

 public:
     virtual ~DeviceSingleWindowEventController();
 
     // Inherited from DeviceEventControllerBase.
     virtual void didUpdateData() override;
     DECLARE_VIRTUAL_TRACE();
 
     // Inherited from DOMWindowLifecycleObserver.
     virtual void didAddEventListener(LocalDOMWindow*, const AtomicString&) override;
     virtual void didRemoveEventListener(LocalDOMWindow*, const AtomicString&) override;
     virtual void didRemoveAllEventListeners(LocalDOMWindow*) override;
 
 protected:
+    explicit DeviceSingleWindowEventController(Document&);
+
     Document& document() const { return *m_document; }
 
-    explicit DeviceSingleWindowEventController(Document&);
-
     void dispatchDeviceEvent(const PassRefPtrWillBeRawPtr<Event>);
 
     virtual PassRefPtrWillBeRawPtr<Event> lastEvent() const = 0;
     virtual const AtomicString& eventTypeName() const = 0;
     virtual bool isNullEvent(Event*) const = 0;
 
 private:
     bool m_needsCheckingNullEvents;
     RawPtrWillBeMember<Document> m_document;
 };
 
 } // namespace blink
 
 #endif // DeviceSingleWindowEventController_h