Implement preference and policy based content settings providers.

chrome/browser/content_settings/content_settings_provider.h

 // Copyright (c) 2010 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 CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_PROVIDER_H_
 #define CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_PROVIDER_H_
 #pragma once
 
 #include "chrome/common/content_settings.h"
 
 class ContentSettingsProviderInterface {
  public:
+  virtual ~ContentSettingsProviderInterface() {}
+
   // True if this provider can provide a default setting for the |content_type|.
-  virtual bool CanProvideDefaultSetting(ContentSettingsType content_type) = 0;
+  virtual bool CanProvideDefaultSetting(
+      ContentSettingsType content_type) const = 0;
 
   // Returns the default content setting this provider has for the given
   // |content_type|, or CONTENT_SETTING_DEFAULT if nothing be provided for this
   // type.
   virtual ContentSetting ProvideDefaultSetting(
-      ContentSettingsType content_type) = 0;
+      ContentSettingsType content_type) const = 0;
 
   // Notifies the provider that the host content settings map would like to
   // update the default setting for the given |content_type|. The provider may
   // ignore this.
   virtual void UpdateDefaultSetting(ContentSettingsType content_type,
                                     ContentSetting setting) = 0;
 
+  // Resets the state of the provider to the default.
+  virtual void ResetToDefaults() = 0;
+
   // True if the default setting for the |content_type| is policy managed, i.e.,
   // there shouldn't be any UI shown to modify this setting.
-  virtual bool DefaultSettingIsManaged(ContentSettingsType content_type) = 0;
-
- protected:
-  virtual ~ContentSettingsProviderInterface() {};
+  virtual bool DefaultSettingIsManaged(
+      ContentSettingsType content_type) const = 0;
 };
 
 #endif  // CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_PROVIDER_H_