Move platform_thread to base/threading and put in the base namespace. I left ...

base/non_thread_safe.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_NON_THREAD_SAFE_H_
 #define BASE_NON_THREAD_SAFE_H_
 #pragma once
 
-#include "base/platform_thread.h"
-#include "base/thread_checker.h"
+#include "base/threading/thread_checker.h"
 
 // A helper class used to help verify that methods of a class are
 // called from the same thread.  One can inherit from this class and use
 // CalledOnValidThread() to verify.
 //
 // This is intended to be used with classes that appear to be thread safe, but
 // aren't.  For example, a service or a singleton like the preferences system.
 //
 // Example:
 // class MyClass : public NonThreadSafe {
@@ skipping 15 matching lines @@
 
  protected:
   // Changes the thread that is checked for in CalledOnValidThread. The next
   // call to CalledOnValidThread will attach this class to a new thread. It is
   // up to the NonThreadSafe derived class to decide to expose this or not.
   // This may be useful when an object may be created on one thread and then
   // used exclusively on another thread.
   void DetachFromThread();
 
  private:
-  ThreadChecker thread_checker_;
+  base::ThreadChecker thread_checker_;
 };
 #else
 // Do nothing in release mode.
 class NonThreadSafe {
  public:
   bool CalledOnValidThread() const {
     return true;
   }
 
  protected:
   void DetachFromThread() {}
 };
 #endif  // NDEBUG
 
 #endif  // BASE_NON_THREAD_SAFE_H_