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

chrome/browser/extensions/extension_settings_frontend.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_FRONTEND_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_FRONTEND_H_
 #pragma once
 
+#include "base/callback.h"
 #include "base/compiler_specific.h"
+#include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
-#include "base/callback.h"
+#include "base/observer_list_threadsafe.h"
+#include "chrome/browser/extensions/extension_settings_observer.h"
 #include "chrome/browser/sync/api/syncable_service.h"
+#include "content/common/notification_observer.h"
+#include "content/common/notification_registrar.h"
 
 class FilePath;
+class Profile;
 class ExtensionSettingsBackend;
 class ExtensionSettingsStorage;
 
 // The component of extension settings which runs on the UI thread, as opposed
 // to ExtensionSettingsBackend which lives on the FILE thread.
-class ExtensionSettingsFrontend {
+class ExtensionSettingsFrontend : public NotificationObserver {
  public:
-  explicit ExtensionSettingsFrontend(const FilePath& base_path);
+  explicit ExtensionSettingsFrontend(Profile* profile);
+  virtual ~ExtensionSettingsFrontend();
 
   typedef base::Callback<void(ExtensionSettingsBackend*)> BackendCallback;
 
   // Runs |callback| on the FILE thread with the extension settings.
   void RunWithBackend(const BackendCallback& callback);
 
-  ~ExtensionSettingsFrontend();
+  // Adds an observer to settings changes.
+  void AddObserver(ExtensionSettingsObserver* observer);
+
+  // Removes an observer to settings changes.
+  void RemoveObserver(ExtensionSettingsObserver* observer);
+
+  // NotificationObserver implementation.
+  virtual void Observe(
+      int type,
+      const NotificationSource& source,
+      const NotificationDetails& details) OVERRIDE;
 
  private:
+  // Called when a profile is created.
+  void OnProfileCreated(Profile* profile);
+
+  // Called when a profile is destroyed.
+  void OnProfileDestroyed(Profile* profile);
+
+  // List of observers to settings changes.
+  scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> > observers_;
+
+  // Map of Profiles to their Observers.  This is so that when Profiles are
+  // destroyed we can remove the associated Observer.
+  // MUST ONLY BE ACCESSED ON THE UI THREAD.
+  class DefaultObserver;
+  std::map<Profile*, linked_ptr<DefaultObserver> > profile_observers_;
+
   // Ref-counted container for the ExtensionSettingsBackend object.
-  class Core : public base::RefCountedThreadSafe<Core> {
-   public:
-    // Constructed on UI thread.
-    Core();
+  class Core;
+  scoped_refptr<Core> core_;
 
-    // Does any FILE thread specific initialization, such as construction of
-    // |backend_|.  Must be called before any call to
-    // RunWithBackendOnFileThread().
-    void InitOnFileThread(const FilePath& base_path);
-
-    // Runs |callback| with the extension backend.
-    void RunWithBackendOnFileThread(const BackendCallback& callback);
-
-   private:
-    // Can be destroyed on either the UI or FILE thread.
-    virtual ~Core();
-    friend class base::RefCountedThreadSafe<Core>;
-
-    // Lives on the FILE thread.
-    ExtensionSettingsBackend* backend_;
-
-    DISALLOW_COPY_AND_ASSIGN(Core);
-  };
-
-  scoped_refptr<Core> core_;
+  // For profile created/destroyed notifications.
+  NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSettingsFrontend);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_FRONTEND_H_