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

chrome/browser/ui/cocoa/screen_capture_notification_ui_cocoa.h

 // Copyright 2013 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.
 
 #import <Cocoa/Cocoa.h>
 
 #include <string>
 
 #include "base/callback.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "chrome/browser/ui/screen_capture_notification_ui.h"
 
 // Controller for the screen capture notification window which allows the user
 // to quickly stop screen capturing.
 @interface ScreenCaptureNotificationController : NSWindowController {
  @private
   base::Closure stop_callback_;
   string16 title_;
   IBOutlet NSTextField* statusField_;
   IBOutlet NSButton* stopButton_;
 }
 
 - (id)initWithCallback:(const base::Closure&)stop_callback
                  title:(const string16&)title;
 - (IBAction)stopSharing:(id)sender;
 @end
 
 // A floating window with a custom border. The custom border and background
 // content is defined by DisconnectView. Declared here so that it can be
 // instantiated via a xib.
 @interface ScreenCaptureNotificationWindow : NSWindow
 @end
 
 // The custom background/border for the ScreenCaptureNotificationWindow.
 // Declared here so that it can be instantiated via a xib.
 @interface ScreenCaptureNotificationView : NSView
 @end