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

ui/base/dragdrop/cocoa_dnd_util.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_DRAGDROP_MAC_DND_UTIL_H_
 #define UI_BASE_DRAGDROP_MAC_DND_UTIL_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <vector>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/ui_export.h"
 
 class GURL;
 
 namespace ui {
 
 // Dummy data type that Chrome places in dragging pasteboards. There is never
 // any data associated with this type; it's only used to ensure that Chrome
 // supports any drag initiated inside of Chrome, whether or not data has been
 // associated with it.
@@ skipping 12 matching lines @@
 // the pasteboard, |NO| otherwise. If |convert_filenames| is |YES|, the function
 // will also attempt to convert filenames in |pboard| to file URLs.
 UI_EXPORT BOOL PopulateURLAndTitleFromPasteboard(GURL* url,
                                                  string16* title,
                                                  NSPasteboard* pboard,
                                                  BOOL convert_filenames);
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_MAC_DND_UTIL_H_