Use a direct include of strings headers in content/p*/.

content/public/browser/web_contents_delegate.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 CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/navigation_type.h"
 #include "content/public/common/media_stream_request.h"
 #include "content/public/common/page_transition_types.h"
 #include "content/public/common/window_container_type.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebDragOperation.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/base/window_open_disposition.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/rect_f.h"
@@ skipping 416 matching lines @@
   // Called when |this| is no longer the WebContentsDelegate for |source|.
   void Detach(WebContents* source);
 
   // The WebContents that this is currently a delegate for.
   std::set<WebContents*> attached_contents_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_