Move the Widget hierarchy to the Oilpan heap.

Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 668 matching lines @@
 
     // The available drag operations (copy, move link...) allowed by the source.
     WebDragOperation m_operationsAllowed;
 
     // The current drag operation as negotiated by the source and destination.
     // When not equal to DragOperationNone, the drag data can be dropped onto the
     // current drop target in this WebView (the drop target can accept the drop).
     WebDragOperation m_dragOperation;
 
     // The popup associated with a select element.
-    RefPtr<PopupContainer> m_selectPopup;
+    RefPtrWillBePersistent<PopupContainer> m_selectPopup;
 
     // The popup associated with an input element.
     RefPtr<WebPagePopupImpl> m_pagePopup;
 
     OwnPtr<WebDevToolsAgentPrivate> m_devToolsAgent;
     OwnPtr<PageOverlayList> m_pageOverlays;
 
     // Whether the webview is rendering transparently.
     bool m_isTransparent;
 
@@ skipping 48 matching lines @@
     float m_topControlsLayoutHeight;
 };
 
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 } // namespace blink
 
 #endif