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

base/threading/thread_checker.h

Index: base/threading/thread_checker.h
===================================================================
--- base/threading/thread_checker.h	(revision 70321)
+++ base/threading/thread_checker.h	(working copy)
@@ -2,15 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef BASE_THREAD_CHECKER_H_
-#define BASE_THREAD_CHECKER_H_
+#ifndef BASE_THREADING_THREAD_CHECKER_H_
+#define BASE_THREADING_THREAD_CHECKER_H_
 #pragma once
 
 #ifndef NDEBUG
 #include "base/lock.h"
-#include "base/platform_thread.h"
+#include "base/threading/platform_thread.h"
 #endif // NDEBUG
 
+namespace base {
+
 // Before using this class, please consider using NonThreadSafe as it
 // makes it much easier to determine the nature of your class.
 //
@@ -66,4 +68,6 @@
 };
 #endif  // NDEBUG
 
-#endif  // BASE_THREAD_CHECKER_H_
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_CHECKER_H_