Use a direct include of strings headers in ui/, part 1.

ui/base/clipboard/clipboard.h

 // Copyright (c) 2012 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_CLIPBOARD_CLIPBOARD_H_
 #define UI_BASE_CLIPBOARD_CLIPBOARD_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/shared_memory.h"
 #include "base/process.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_checker.h"
 #include "ui/base/ui_export.h"
 
 #if defined(TOOLKIT_GTK)
 #include <gdk/gdk.h>
 #endif
 
 #if defined(OS_WIN)
 #include <objidl.h>
@@ skipping 372 matching lines @@
   class AuraX11Details;
   scoped_ptr<AuraX11Details> aurax11_details_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(Clipboard);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_CLIPBOARD_CLIPBOARD_H_