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

webkit/common/webpreferences.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.
 //
 // A struct for managing webkit's settings.
 //
 // Adding new values to this class probably involves updating
 // WebKit::WebSettings, content/common/view_messages.h, browser/tab_contents/
 // render_view_host_delegate_helper.cc, and browser/profiles/profile.cc.
 
 #ifndef WEBKIT_COMMON_WEBPREFERENCES_H__
 #define WEBKIT_COMMON_WEBPREFERENCES_H__
 
 #include <map>
 #include <string>
 #include <vector>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "googleurl/src/gurl.h"
 #include "webkit/common/webkit_common_export.h"
 
 namespace WebKit {
 class WebView;
 }
 
 struct WebPreferences;
 
 namespace webkit_glue {
@@ skipping 143 matching lines @@
 #endif
 
   // We try to keep the default values the same as the default values in
   // chrome, except for the cases where it would require lots of extra work for
   // the embedder to use the same default value.
   WebPreferences();
   ~WebPreferences();
 };
 
 #endif  // WEBKIT_COMMON_WEBPREFERENCES_H__