Remove unnecessary use of CrossThreadPersistent<>.

third_party/WebKit/Source/web/WebFrameWidgetImpl.h

 /*
  * Copyright (C) 2014 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 193 matching lines @@
 
     WebSize m_size;
 
     // If set, the (plugin) node which has mouse capture.
     Member<Node> m_mouseCaptureNode;
     RefPtr<UserGestureToken> m_mouseCaptureGestureToken;
 
     // This is owned by the LayerTreeHostImpl, and should only be used on the
     // compositor thread. The LayerTreeHostImpl is indirectly owned by this
     // class so this pointer should be valid until this class is destructed.
-    CrossThreadPersistent<CompositorMutatorImpl> m_mutator;
+    Member<CompositorMutatorImpl> m_mutator;
 
     WebLayerTreeView* m_layerTreeView;
     WebLayer* m_rootLayer;
     GraphicsLayer* m_rootGraphicsLayer;
     bool m_isAcceleratedCompositingActive;
     bool m_layerTreeViewClosed;
 
     bool m_suppressNextKeypressEvent;
 
     bool m_ignoreInputEvents;
 
     // Whether the WebFrameWidget is rendering transparently.
     bool m_isTransparent;
 
     static const WebInputEvent* m_currentInputEvent;
 
     WebColor m_baseBackgroundColor;
 
     SelfKeepAlive<WebFrameWidgetImpl> m_selfKeepAlive;
 };
 
 DEFINE_TYPE_CASTS(WebFrameWidgetImpl, WebFrameWidget, widget, widget->forSubframe(), widget.forSubframe());
 
 } // namespace blink
 
 #endif