Use a direct include of strings headers in chrome/browser/ui/a*/.

chrome/browser/ui/app_modal_dialogs/app_modal_dialog.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 CHROME_BROWSER_UI_APP_MODAL_DIALOGS_APP_MODAL_DIALOG_H_
 #define CHROME_BROWSER_UI_APP_MODAL_DIALOGS_APP_MODAL_DIALOG_H_
 
 #include <string>
 
 #include "base/basictypes.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "build/build_config.h"
 
 class NativeAppModalDialog;
 
 namespace content {
 class WebContents;
 }
 
 // A controller+model base class for modal dialogs.
 class AppModalDialog {
@@ skipping 60 matching lines @@
 
   // The toolkit-specific implementation of the app modal dialog box.
   NativeAppModalDialog* native_dialog_;
 
   content::WebContents* web_contents_;
 
   DISALLOW_COPY_AND_ASSIGN(AppModalDialog);
 };
 
 #endif  // CHROME_BROWSER_UI_APP_MODAL_DIALOGS_APP_MODAL_DIALOG_H_