content: Cleanup class/struct forward declarations

components/guest_view/browser/guest_view_manager.h

 // Copyright 2014 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 COMPONENTS_GUEST_VIEW_BROWSER_GUEST_VIEW_MANAGER_H_
 #define COMPONENTS_GUEST_VIEW_BROWSER_GUEST_VIEW_MANAGER_H_
 
 #include <map>
 #include <memory>
 #include <set>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "content/public/browser/browser_plugin_guest_manager.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
 
 class GURL;
 
+namespace base {
+class DictionaryValue;
+}
+
 namespace content {
 class BrowserContext;
 class WebContents;
 }  // namespace content
 
 namespace guest_view {
 
 class GuestViewBase;
 class GuestViewManagerDelegate;
 class GuestViewManagerFactory;
@@ skipping 237 matching lines @@
   // call into this GuestViewManager after it has been destroyed.
   base::WeakPtrFactory<GuestViewManager> weak_ptr_factory_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GuestViewManager);
 };
 
 }  // namespace guest_view
 
 #endif  // COMPONENTS_GUEST_VIEW_BROWSER_GUEST_VIEW_MANAGER_H_