Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.cc

Index: chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.cc
diff --git a/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.cc b/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4c916b44d0793661ccf52be5eb8fd5e6751a2b0b
--- /dev/null
+++ b/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.cc
@@ -0,0 +1,87 @@
+// 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.
+
+// MediaGalleryExtensionNotificationObserver implementation.
+
+#include "chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h"
+
+#include <string>
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager.h"
+#include "chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager_factory.h"
+#include "chrome/browser/extensions/extension_host.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/extensions/extension.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_details.h"
+#include "content/public/browser/notification_service.h"
+
+namespace extensions {
+
+using content::BrowserThread;
+
+namespace {
+
+// Handles the extension destroyed event on the file thread.
+void HandleExtensionDestroyedOnFileThread(const Profile* profile,
+                                          const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  if (!GalleryWatchManagerFactory::GetInstance()->HasForProfile(profile))
+    return;
+  GalleryWatchManager* manager =
+      GalleryWatchManagerFactory::GetInstance()->GetForProfile(profile);
+  if (!manager)

[Lei Zhang, 2012/12/15 01:11:54]

How can this happen when HasForProfile() just returned true?

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

You are right. |manager| can never be null here. Fixed.

+    return;
+  manager->OnExtensionDestroyed(extension_id);
+}
+
+}  // namespace
+
+MediaGalleryExtensionNotificationObserver::
+MediaGalleryExtensionNotificationObserver(Profile* profile)
+    : profile_(profile) {
+  DCHECK(profile_);
+  registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED,
+                 content::Source<Profile>(profile_->GetOriginalProfile()));
+  registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_UNLOADED,
+                 content::Source<Profile>(profile_->GetOriginalProfile()));
+}
+
+MediaGalleryExtensionNotificationObserver::
+~MediaGalleryExtensionNotificationObserver() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void MediaGalleryExtensionNotificationObserver::Observe(
+    int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
+    const Extension* extension =
+        content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
+    content::BrowserThread::PostTask(
+        content::BrowserThread::FILE, FROM_HERE,
+        base::Bind(&HandleExtensionDestroyedOnFileThread,
+                   profile_,
+                   extension->id()));
+
+  } else if (type == chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED) {
+    ExtensionHost* host = content::Details<ExtensionHost>(details).ptr();
+    const Extension* extension = host->extension();
+    content::BrowserThread::PostTask(

[Lei Zhang, 2012/12/15 01:11:54]

This block looks a lot like the previous one. You can simplify this to:

Extension* extension = NULL;
if (type == A) {
  ...
  extension = foo;
} else if (type == B) {
  ...
  extension = bar;
}
DCHECK(extension);
PostTask(...);

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

Done.

+        content::BrowserThread::FILE, FROM_HERE,
+        base::Bind(&HandleExtensionDestroyedOnFileThread,
+                   profile_,
+                   extension->id()));
+
+  } else {
+    NOTREACHED();

[Lei Zhang, 2012/12/15 01:11:54]

You don't need this. You can write the code as:
if (type == A) {
  ...
} else {
  DCHECK_EQ(B, type);
  ...
}

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

Done.

+  }
+ }
+
+}  // namespace extensions