Cleanup namespace usage in Source/core/{dom/* & fileapi/*}

Source/core/dom/ExecutionContext.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2012 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
@@ skipping 310 matching lines @@
         m_client->securityContext().setSecurityOrigin(SecurityOrigin::createUnique());
         m_client->didUpdateSecurityOrigin();
     }
 }
 
 void ExecutionContext::trace(Visitor* visitor)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_pendingExceptions);
 #endif
-    WillBeHeapSupplementable<blink::ExecutionContext>::trace(visitor);
+    WillBeHeapSupplementable<ExecutionContext>::trace(visitor);
 }
 
 } // namespace blink