Add onChanged events to the extension settings API, both from sync and between

chrome/browser/extensions/extension_settings_backend.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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_BACKEND_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_BACKEND_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
+#include "base/observer_list_threadsafe.h"
 #include "base/task.h"
+#include "chrome/browser/extensions/extension_settings_observer.h"
 #include "chrome/browser/extensions/syncable_extension_settings_storage.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 
 // Manages ExtensionSettingsStorage objects for extensions, including routing
 // changes from sync to them.
 // Lives entirely on the FILE thread.
 class ExtensionSettingsBackend : public SyncableService {
  public:
-  // File path is the base of the extension settings directory.
-  // The databases will be at base_path/extension_id.
-  explicit ExtensionSettingsBackend(const FilePath& base_path);
+  // |base_path| is the base of the extension settings directory, so the
+  // databases will be at base_path/extension_id.
+  // |observers| is the list of observers to settings changes.
+  explicit ExtensionSettingsBackend(
+      const FilePath& base_path,
+      const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >&
+          observers);
 
   virtual ~ExtensionSettingsBackend();
 
   // Gets a weak reference to the storage area for a given extension.
   // Must be run on the FILE thread.
   //
   // By default this will be an ExtensionSettingsLeveldbStorage, but on
   // failure to create a leveldb instance will fall back to
   // InMemoryExtensionSettingsStorage.
   ExtensionSettingsStorage* GetStorage(
       const std::string& extension_id) const;
 
   // Deletes all setting data for an extension.  Call on the FILE thread.
   void DeleteExtensionData(const std::string& extension_id);
 
+  // Sends a change event to the observer list.  |profile| is the profile which
+  // generated the change.  Must be called on the FILE thread.
+  void TriggerOnSettingsChanged(
+      Profile* profile,
+      const std::string& extension_id,
+      const ExtensionSettingsChanges& changes) const;
+
   // SyncableService implementation.
   virtual SyncDataList GetAllSyncData(syncable::ModelType type) const OVERRIDE;
   virtual SyncError MergeDataAndStartSyncing(
       syncable::ModelType type,
       const SyncDataList& initial_sync_data,
       SyncChangeProcessor* sync_processor) OVERRIDE;
   virtual SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
       const SyncChangeList& change_list) OVERRIDE;
   virtual void StopSyncing(syncable::ModelType type) OVERRIDE;
 
  private:
   // Gets a weak reference to the storage area for a given extension,
   // initializing sync with some initial data if sync enabled.
   //
   // By default this will be of a cached LEVELDB storage, but on failure to
   // create a leveldb instance will fall back to cached NOOP storage.
   SyncableExtensionSettingsStorage* GetOrCreateStorageWithSyncData(
       const std::string& extension_id, const DictionaryValue& sync_data) const;
 
   // Gets all extension IDs known to extension settings.  This may not be all
   // installed extensions.
   std::set<std::string> GetKnownExtensionIDs() const;
 
   // The base file path to create any leveldb databases at.
   const FilePath base_path_;
 
+  // The list of observers to settings changes.
+  const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >
+      observers_;
+
   // A cache of ExtensionSettingsStorage objects that have already been created.
   // Ensure that there is only ever one created per extension.
   typedef std::map<std::string, linked_ptr<SyncableExtensionSettingsStorage> >
       StorageObjMap;
   mutable StorageObjMap storage_objs_;
 
   // Current sync processor, if any.
   SyncChangeProcessor* sync_processor_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSettingsBackend);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_BACKEND_H_