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

base/debug/debugger.cc

 // 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.
 
 #include "base/debug/debugger.h"
 
-#include "base/platform_thread.h"
+#include "base/threading/platform_thread.h"
 
 namespace base {
 namespace debug {
 
 bool WaitForDebugger(int wait_seconds, bool silent) {
   for (int i = 0; i < wait_seconds * 10; ++i) {
     if (BeingDebugged()) {
       if (!silent)
         BreakDebugger();
       return true;
     }
     PlatformThread::Sleep(100);
   }
   return false;
 }
 
 }  // namespace debug
 }  // namespace base