Detach the dependency from host_content_settings_map to extension.

chrome/browser/content_settings/host_content_settings_map.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.
 
 // Maps hostnames to custom content settings.  Written on the UI thread and read
 // on any thread.  One instance per profile.
 
 #ifndef CHROME_BROWSER_CONTENT_SETTINGS_HOST_CONTENT_SETTINGS_MAP_H_
 #define CHROME_BROWSER_CONTENT_SETTINGS_HOST_CONTENT_SETTINGS_MAP_H_
 
@@ skipping 15 matching lines @@
 class ExtensionService;
 class GURL;
 class PrefService;
 
 namespace base {
 class Clock;
 class Value;
 }
 
 namespace content_settings {
+class ObservableProvider;
 class ProviderInterface;
 class PrefProvider;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 class HostContentSettingsMap
     : public content_settings::Observer,
       public base::RefCountedThreadSafe<HostContentSettingsMap> {
  public:
   enum ProviderType {
+    // EXTENSION names is a layering violation when this class will move to
+    // components.
+    // TODO(mukai): find the solution.
     INTERNAL_EXTENSION_PROVIDER = 0,
     POLICY_PROVIDER,
     CUSTOM_EXTENSION_PROVIDER,
     PREF_PROVIDER,
     DEFAULT_PROVIDER,
     NUM_PROVIDER_TYPES,
   };
 
   HostContentSettingsMap(PrefService* prefs, bool incognito);
 
-#if defined(ENABLE_EXTENSIONS)
-  // In some cases, the ExtensionService is not available at the time the
-  // HostContentSettingsMap is constructed. In these cases, we register the
-  // service once it's available.
-  void RegisterExtensionService(ExtensionService* extension_service);
-#endif
+  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
-  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
+  // Adds a new provider for |type|.
+  void RegisterProvider(
+      ProviderType type,
+      scoped_ptr<content_settings::ObservableProvider> provider);
 
   // Returns the default setting for a particular content type. If |provider_id|
   // is not NULL, the id of the provider which provided the default setting is
   // assigned to it.
   //
   // This may be called on any thread.
   ContentSetting GetDefaultContentSetting(ContentSettingsType content_type,
                                           std::string* provider_id) const;
 
   // Returns a single |ContentSetting| which applies to the given URLs.  Note
@@ skipping 237 matching lines @@
   // time and by RegisterExtensionService, both of which should happen
   // before any other uses of it.
   ProviderMap content_settings_providers_;
 
   ObserverList<content_settings::Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(HostContentSettingsMap);
 };
 
 #endif  // CHROME_BROWSER_CONTENT_SETTINGS_HOST_CONTENT_SETTINGS_MAP_H_