Fixed all unused-variable Clang warnings on Windows.

ui/base/win/atl_module.h

 // Copyright (c) 2011 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 UI_BASE_WIN_ATL_MODULE_H_
 #define UI_BASE_WIN_ATL_MODULE_H_
 
 #include <atlbase.h>
 #include <atlcom.h>
 
 #include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/macros.h"
 
 namespace ui {
 namespace win {
 
 // Ensure that we have exactly one ATL module registered. It's safe to
 // call this more than once. ATL functions will crash if there's no
 // ATL module registered, or if you try to register two of them, so
 // dynamically registering one if needed makes it much easier for us
 // to support different build configurations like multi-dll without
 // worrying about which side of a module boundary each ATL module object
 // belongs on.
 //
 // This function must be implemented in this header file rather than a
 // source file so that it's inlined into the module where it's included,
 // rather than in the "ui" module.
 static void CreateATLModuleIfNeeded() {
   if (_pAtlModule == NULL) {
     // This creates the module and automatically updates _pAtlModule.
     CR_DEFINE_STATIC_LOCAL(CComModule, module, ());
+    ALLOW_UNUSED_LOCAL(module);
   }
 }
 
 }  // namespace win
 }  // namespace ui
 
 #endif  // UI_BASE_WIN_ATL_MODULE_H_