Cleanup namespace usage in Source/core/platform/[A-Z]*.h

Source/platform/Task.h

 /*
  * Copyright (C) 2013 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 18 matching lines @@
  */
 
 #ifndef Task_h
 #define Task_h
 
 #include "public/platform/WebThread.h"
 #include "wtf/Functional.h"
 
 namespace blink {
 
-class Task : public blink::WebThread::Task {
+class Task : public WebThread::Task {
 public:
     explicit Task(const Closure& closure)
         : m_closure(closure)
     {
     }
 
     virtual void run() OVERRIDE
     {
         m_closure();
     }
 
 private:
     Closure m_closure;
 };
 
 } // namespace blink
 
 #endif // Task_h