chrome: Cleanup class/struct forward declarations

chrome/browser/android/webapps/single_tab_mode_tab_helper.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.
 
 #ifndef CHROME_BROWSER_ANDROID_WEBAPPS_SINGLE_TAB_MODE_TAB_HELPER_H_
 #define CHROME_BROWSER_ANDROID_WEBAPPS_SINGLE_TAB_MODE_TAB_HELPER_H_
 
 #include <stdint.h>
 
 #include <set>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "chrome/browser/ui/blocked_content/blocked_window_params.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
 class RenderViewHost;
 class WebContents;
 }  // namespace content
 
-class GURL;
-
 // Registers and unregisters the IDs of renderers in single tab mode, which
 // are disallowed from opening new windows via
 // ChromeContentBrowserClient::CanCreateWindow().
 class SingleTabModeTabHelper
     : public content::WebContentsObserver,
       public content::WebContentsUserData<SingleTabModeTabHelper> {
  public:
   // Checks if the ID pair is blocked from creating new windows. IO-thread only.
   static bool IsRegistered(int32_t process_id, int32_t routing_id);
 
@@ skipping 13 matching lines @@
  private:
   explicit SingleTabModeTabHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SingleTabModeTabHelper>;
 
   bool block_all_new_windows_;
 
   DISALLOW_COPY_AND_ASSIGN(SingleTabModeTabHelper);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_WEBAPPS_SINGLE_TAB_MODE_TAB_HELPER_H_