Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api.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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERIES_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERIES_PRIVATE_API_H_
 
+#include <string>
+
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/extensions/event_router.h"
+#include "chrome/browser/extensions/extension_function.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 
+class FilePath;
+class Profile;
+
 namespace extensions {
+
+class MediaGalleryExtensionNotificationObserver;
 class MediaGalleriesPrivateEventRouter;
 
+// The profile-keyed service that manages the media galleries private extension
+// API.
 class MediaGalleriesPrivateAPI : public ProfileKeyedService,
-                                 public extensions::EventRouter::Observer {
+                                 public EventRouter::Observer {
  public:
   explicit MediaGalleriesPrivateAPI(Profile* profile);
   virtual ~MediaGalleriesPrivateAPI();
 
   // ProfileKeyedService implementation.
   virtual void Shutdown() OVERRIDE;
 
   // EventRouter::Observer implementation.
-  virtual void OnListenerAdded(const extensions::EventListenerInfo& details)
-      OVERRIDE;
+  virtual void OnListenerAdded(const EventListenerInfo& details) OVERRIDE;
+
+  MediaGalleriesPrivateEventRouter* event_router() const {
+    return media_galleries_private_event_router_.get();
+  }
 
  private:
+  // Current profile.
   Profile* profile_;
 
+  scoped_ptr<MediaGalleryExtensionNotificationObserver>

[Lei Zhang, 2012/12/15 04:13:21]

Why both with a separate observer? Composition isn't always the right solution.
There's 300+ classes that all inherit from content::NotificationObserver. Very
few of them create a separate observer class.

[kmadhusu, 2012/12/17 23:58:05]

GalleryWatchManager needs to perform some clean up operations when an extension
is destroyed. GalleryWatchManager lives on the file thread.
NotificationObserver::Observe function is called on the UI thread. If
GalleryWatchManager inherits from NotificationObserver, we are introducing a
function in GalleryWatchManager which gets called on the UI thread. I have to
either use a lock or weak pointer to do the clean up operations. Inheritance
solution makes this complex. With composition, it is simple and easier to
understand and manage the objects.

+      extension_notification_observer_;
+
+  // Created lazily on first access.
   scoped_ptr<MediaGalleriesPrivateEventRouter>
       media_galleries_private_event_router_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaGalleriesPrivateAPI);
+};
+
+class MediaGalleryWatchFunctionBase : public AsyncExtensionFunction {
+ protected:
+  MediaGalleryWatchFunctionBase();
+  virtual ~MediaGalleryWatchFunctionBase() {}
+
+  virtual void PerformGalleryWatchOperation(
+      const std::string& gallery_id,
+      const FilePath& gallery_watch_path) = 0;
+
+  // Gallery watch request handler.
+  virtual void HandleResponse(const std::string& gallery_id,
+                              bool success) = 0;
+
+  // AsyncExtensionFunction overrides.
+  virtual bool RunImpl() OVERRIDE;
+};
+
+// Implements the chrome.mediaGalleriesPrivate.addGalleryWatch method.
+class MediaGalleriesPrivateAddGalleryWatchFunction
+    : public MediaGalleryWatchFunctionBase {
+ public:
+  DECLARE_EXTENSION_FUNCTION_NAME("mediaGalleriesPrivate.addGalleryWatch");
+
+ protected:
+  virtual ~MediaGalleriesPrivateAddGalleryWatchFunction() {}
+
+  virtual void PerformGalleryWatchOperation(
+      const std::string& gallery_id,
+      const FilePath& gallery_watch_path) OVERRIDE;
+  virtual void HandleResponse(const std::string& gallery_id,
+                              bool success) OVERRIDE;
+};
+
+// Implements the chrome.mediaGalleriesPrivate.removeGalleryWatch method.
+class MediaGalleriesPrivateRemoveGalleryWatchFunction

[Lei Zhang, 2012/12/15 02:00:29]

I don't think the two Function classes should share a base class. Unlike the
AddGalleryWatch, RemoveGalleryWatch is synchronous. The only thing
MediaGalleriesPrivateRemoveGalleryWatchFunction::HandleResponse() does is return
true, and you can just do that in RunImpl().

[kmadhusu, 2012/12/17 23:58:05]

Good catch. Fixed.

+    : public MediaGalleryWatchFunctionBase {
+ public:
+  DECLARE_EXTENSION_FUNCTION_NAME("mediaGalleriesPrivate.removeGalleryWatch");
+
+ protected:
+  virtual ~MediaGalleriesPrivateRemoveGalleryWatchFunction() {}
+
+  virtual void PerformGalleryWatchOperation(
+      const std::string& gallery_id,
+      const FilePath& gallery_watch_path) OVERRIDE;
+  virtual void HandleResponse(const std::string& gallery_id,
+                              bool success) OVERRIDE;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERIES_PRIVATE_API_H_