components: Cleanup class/struct fwd declarations

components/content_settings/core/browser/content_settings_provider.h

 // Copyright (c) 2011 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.
 
 // Interface for objects providing content setting rules.
 
 #ifndef COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_PROVIDER_H_
 #define COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_PROVIDER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/values.h"
 #include "components/content_settings/core/browser/content_settings_rule.h"
 #include "components/content_settings/core/common/content_settings.h"
 
 class ContentSettingsPattern;
 
 namespace content_settings {
 
-struct Rule;
 class RuleIterator;
 
 class ProviderInterface {
  public:
   virtual ~ProviderInterface() {}
 
   // Returns a |RuleIterator| over the content setting rules stored by this
   // provider. If |incognito| is true, the iterator returns only the content
   // settings which are applicable to the incognito mode and differ from the
   // normal mode. Otherwise, it returns the content settings for the normal
@@ skipping 32 matching lines @@
   // Detaches the Provider from all Profile-related objects like PrefService.
   // This methods needs to be called before destroying the Profile.
   // Afterwards, none of the methods above that should only be called on the UI
   // thread should be called anymore.
   virtual void ShutdownOnUIThread() = 0;
 };
 
 }  // namespace content_settings
 
 #endif  // COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_PROVIDER_H_