Move the Widget hierarchy to the Oilpan heap.

Source/web/WebPluginContainerImpl.h

Index: Source/web/WebPluginContainerImpl.h
diff --git a/Source/web/WebPluginContainerImpl.h b/Source/web/WebPluginContainerImpl.h
index 5ff3dcaf5a794f24ed46f98530be968f5bdd365e..19e42f49a6f9d972ea153b2c451b9b0eff46a1ba 100644
--- a/Source/web/WebPluginContainerImpl.h
+++ b/Source/web/WebPluginContainerImpl.h
@@ -54,6 +54,7 @@ class MouseEvent;
 class PlatformGestureEvent;
 class ResourceError;
 class ResourceResponse;
+class ScriptController;
 class ScrollbarGroup;
 class TouchEvent;
 class WebPlugin;
@@ -63,17 +64,12 @@ class WheelEvent;
 class Widget;
 struct WebPrintParams;
 
-class WebPluginContainerImpl FINAL
-    : public PluginView
-    , public WebPluginContainer
-#if !ENABLE(OILPAN)
-    , public FrameDestructionObserver
-#endif
-    {
+class WebPluginContainerImpl FINAL : public PluginView, public WebPluginContainer, public FrameDestructionObserver {
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(WebPluginContainerImpl);
 public:
-    static PassRefPtr<WebPluginContainerImpl> create(HTMLPlugInElement* element, WebPlugin* webPlugin)
+    static PassRefPtrWillBeRawPtr<WebPluginContainerImpl> create(HTMLPlugInElement* element, WebPlugin* webPlugin)
     {
-        return adoptRef(new WebPluginContainerImpl(element, webPlugin));
+        return adoptRefWillBeNoop(new WebPluginContainerImpl(element, webPlugin));
     }
 
     // PluginView methods
@@ -169,9 +165,8 @@ public:
 
     bool paintCustomOverhangArea(GraphicsContext*, const IntRect&, const IntRect&, const IntRect&);
 
-#if ENABLE(OILPAN)
-    virtual void detach() OVERRIDE;
-#endif
+    virtual void trace(Visitor*) OVERRIDE;
+    virtual void dispose() OVERRIDE;
 
 private:
     WebPluginContainerImpl(HTMLPlugInElement*, WebPlugin*);
@@ -198,24 +193,14 @@ private:
         const IntRect& frameRect,
         Vector<IntRect>& cutOutRects);
 
-#if ENABLE(OILPAN)
-    // FIXME: Oilpan: consider moving Widget to the heap, allowing this
-    // container object to be a FrameDestructionObserver. And thereby
-    // keep a traced member reference to the frame rather than as a
-    // bare pointer. Instead, the owning object (HTMLFrameOwnerElement)
-    // explicitly deletes this object when it is disconnected from its
-    // frame. Any access to an invalid frame via this bare pointer
-    // is therefore not possible.
+    // Oilpan: this is kept as a bare pointer to support renderer-less
+    // persisted plugins and their finalization. To handle that
+    // step correctly, an untraced reference is kept; see
+    // HTMLPlugInElement::m_persistedPluginWidget comment.
     //
-    // See the HTMLFrameOwnerElement::disconnectContentFrame comment for
-    // (even) more.
-    LocalFrame* m_frame;
-
-    LocalFrame* frame() const { return m_frame; }
-#endif
-
-    // FIXME: see above; for the time being, a bare pointer to the owning
-    // HTMLPlugInElement and managed as such.
+    // Note: using a traced Member<> would create a direct cycle
+    // with m_persistedPluginWidget, hence not done. A weak member
+    // is an alternative, but it is not unsafe to use a bare pointer.
     HTMLPlugInElement* m_element;
     WebPlugin* m_webPlugin;
     Vector<WebPluginLoadObserver*> m_pluginLoadObservers;