chrome: Cleanup class/struct forward declarations

chrome/browser/ui/views/extensions/extension_popup.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 CHROME_BROWSER_UI_VIEWS_EXTENSIONS_EXTENSION_POPUP_H_
 #define CHROME_BROWSER_UI_VIEWS_EXTENSIONS_EXTENSION_POPUP_H_
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
 #include "chrome/browser/ui/views/extensions/extension_view_views.h"
 #include "content/public/browser/devtools_agent_host_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/views/bubble/bubble_dialog_delegate.h"
 #include "url/gurl.h"
 
-
-class Browser;
 namespace views {
 class Widget;
 }
 
 namespace content {
 class DevToolsAgentHost;
 }
 
 namespace extensions {
 class ExtensionViewHost;
@@ skipping 92 matching lines @@
   bool inspect_with_devtools_;
 
   content::NotificationRegistrar registrar_;
 
   bool widget_initialized_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionPopup);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_EXTENSIONS_EXTENSION_POPUP_H_