ios: Cleanup class/struct forward declarations

ios/web/public/web_ui_ios_data_source.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 IOS_WEB_PUBLIC_WEB_UI_IOS_DATA_SOURCE_H_
 #define IOS_WEB_PUBLIC_WEB_UI_IOS_DATA_SOURCE_H_
 
 #include "base/callback.h"
 #include "base/strings/string16.h"
 #include "base/supports_user_data.h"
 
-namespace base {
-class DictionaryValue;
-class RefCountedMemory;
-}
-
 namespace web {
 class BrowserState;
 
 // A data source that can help with implementing the common operations needed by
 // WebUIIOS pages.
 class WebUIIOSDataSource : public base::SupportsUserData {
  public:
   ~WebUIIOSDataSource() override {}
 
   static WebUIIOSDataSource* Create(const std::string& source_name);
@@ skipping 24 matching lines @@
   // Sets the resource to returned when no other paths match.
   virtual void SetDefaultResource(int resource_id) = 0;
 
   // The following map to methods on URLDataSource. See the documentation there.
   virtual void DisableDenyXFrameOptions() = 0;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_WEB_UI_IOS_DATA_SOURCE_H_