Oilpan: have Navigator and its supplements be on the heap by default.

Source/modules/gamepad/NavigatorGamepad.h

 /*
  * Copyright (C) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 24 matching lines @@
 #include "platform/heap/Handle.h"
 #include "public/platform/WebGamepads.h"
 
 namespace blink {
 
 class Document;
 class Gamepad;
 class GamepadList;
 class Navigator;
 
-class MODULES_EXPORT NavigatorGamepad final : public NoBaseWillBeGarbageCollectedFinalized<NavigatorGamepad>, public WillBeHeapSupplement<Navigator>, public DOMWindowProperty, public PlatformEventController, public DOMWindowLifecycleObserver {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(NavigatorGamepad);
+// TODO(Oilpan): when ~DOMWindowProperty is removed, derive from GarbageCollected<> instead.

[haraken, 2015/04/24 15:32:36]

Can we move these comments to DOMWindowProperty and remove them from each
subclass? I guess we'll need to add more comments in the future.

[sof, 2015/04/24 21:25:08]

Done; I considered some time ago adding DOMWindowPropertyGarbageCollected which
would be a GarbageCollectedMixin, but I don't think the churn is worth it.

+class MODULES_EXPORT NavigatorGamepad final : public GarbageCollectedFinalized<NavigatorGamepad>, public HeapSupplement<Navigator>, DOMWindowProperty, public PlatformEventController, public DOMWindowLifecycleObserver {
+    USING_GARBAGE_COLLECTED_MIXIN(NavigatorGamepad);
 public:
     static NavigatorGamepad* from(Document&);
     static NavigatorGamepad& from(Navigator&);
     virtual ~NavigatorGamepad();
 
     static GamepadList* getGamepads(Navigator&);
     GamepadList* gamepads();
 
     DECLARE_VIRTUAL_TRACE();
 
@@ skipping 17 matching lines @@
     virtual void unregisterWithDispatcher() override;
     virtual bool hasLastData() override;
     virtual void didUpdateData() override;
     virtual void pageVisibilityChanged() override;
 
     // DOMWindowLifecycleObserver
     virtual void didAddEventListener(LocalDOMWindow*, const AtomicString&) override;
     virtual void didRemoveEventListener(LocalDOMWindow*, const AtomicString&) override;
     virtual void didRemoveAllEventListeners(LocalDOMWindow*) override;
 
-    PersistentWillBeMember<GamepadList> m_gamepads;
-    PersistentHeapDequeWillBeHeapDeque<Member<Gamepad>> m_pendingEvents;
+    Member<GamepadList> m_gamepads;
+    HeapDeque<Member<Gamepad>> m_pendingEvents;
     AsyncMethodRunner<NavigatorGamepad> m_dispatchOneEventRunner;

[haraken, 2015/04/24 15:37:17]

It seems that AsyncMethodRunner is not safe for lazy sweeping. I think we need
to implement the isHeapObjectAlive logic we implemented for Timer::fired()
(https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...)
for AsyncMethodRunner::fired() as well.

[sof, 2015/04/24 15:40:10]

You have looked at the comment next to AsyncMethodRunner::m_object ?

[haraken, 2015/04/24 15:44:44]

That is a different issue than the issue mentioned in the comment.

AsyncMethodRunner::fired() can call a function that can touch other on-heap
objects that have been already swept in the lazy sweeping. If the m_object is
going to be swept soon in the current lazy sweeping, we should avoid invoking
the fired() method. You've taken care of the problem for Timer by implementing
TimerIsObjectAliveTrait, and I think we need the same mechanism here.

[sof, 2015/04/24 15:55:13]

Thanks, now I remember the non-local nature of this problem. I suppose we would
get it for "free" if AsyncMethodRunner was on the heap -- it's Timer would then
do the check before firing.

[sof, 2015/04/24 21:25:08]

Addressing this one via https://codereview.chromium.org/1108663002/

 };
 
 } // namespace blink
 
 #endif // NavigatorGamepad_h