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

ui/base/clipboard/scoped_clipboard_writer.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.
 
 // This file declares the ScopedClipboardWriter class, a wrapper around
 // the Clipboard class which simplifies writing data to the system clipboard.
 // Upon deletion the class atomically writes all data to |clipboard_|,
 // avoiding any potential race condition with other processes that are also
 // writing to the system clipboard.
 
 #ifndef UI_BASE_CLIPBOARD_SCOPED_CLIPBOARD_WRITER_H_
 #define UI_BASE_CLIPBOARD_SCOPED_CLIPBOARD_WRITER_H_
 
 #include <string>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/clipboard/clipboard.h"
 #include "ui/base/ui_export.h"
 
 class Pickle;
 
 namespace ui {
 
 // This class is a wrapper for |Clipboard| that handles packing data
 // into a Clipboard::ObjectMap.
 // NB: You should probably NOT be using this class if you include
@@ skipping 57 matching lines @@
   std::string url_text_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScopedClipboardWriter);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_CLIPBOARD_SCOPED_CLIPBOARD_WRITER_H_