Remove unnecessary use of CrossThreadPersistent<>.

third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp

 /*
  * 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 103 matching lines @@
 }
 
 WebFrameWidgetImpl::~WebFrameWidgetImpl()
 {
 }
 
 DEFINE_TRACE(WebFrameWidgetImpl)
 {
     visitor->trace(m_localRoot);
     visitor->trace(m_mouseCaptureNode);
+    visitor->trace(m_mutator);
 }
 
 // WebWidget ------------------------------------------------------------------
 
 void WebFrameWidgetImpl::close()
 {
     WebDevToolsAgentImpl::webFrameWidgetImplClosed(this);
     DCHECK(allInstances().contains(this));
     allInstances().remove(this);
 
@@ skipping 992 matching lines @@
 
 HitTestResult WebFrameWidgetImpl::hitTestResultForRootFramePos(const IntPoint& posInRootFrame)
 {
     IntPoint docPoint(m_localRoot->frame()->view()->rootFrameToContents(posInRootFrame));
     HitTestResult result = m_localRoot->frame()->eventHandler().hitTestResultAtPoint(docPoint, HitTestRequest::ReadOnly | HitTestRequest::Active);
     result.setToShadowHostIfInUserAgentShadowRoot();
     return result;
 }
 
 } // namespace blink