Made it possible to tell whether an extension is being installed or updated.

chrome/browser/sync_file_system/sync_file_system_service.cc

 // 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.
 
 #include "chrome/browser/sync_file_system/sync_file_system_service.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 433 matching lines @@
 }
 
 void SyncFileSystemService::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   // Event notification sequence.
   //
   // (User action)    (Notification type)
   // Install:         INSTALLED.
+  // Update:          INSTALLED.
   // Uninstall:       UNLOADED(UNINSTALL).
   // Launch, Close:   No notification.
   // Enable:          EABLED.
   // Disable:         UNLOADED(DISABLE).
   // Reload, Restart: UNLOADED(DISABLE) -> INSTALLED -> ENABLED.
   //
   switch (type) {
     case chrome::NOTIFICATION_EXTENSION_INSTALLED:
       HandleExtensionInstalled(details);
       break;
     case chrome::NOTIFICATION_EXTENSION_UNLOADED:
       HandleExtensionUnloaded(type, details);
       break;
     case chrome::NOTIFICATION_EXTENSION_ENABLED:
       HandleExtensionEnabled(type, details);
       break;
     default:
       NOTREACHED() << "Unknown notification.";
       break;
   }
 }
 
 void SyncFileSystemService::HandleExtensionInstalled(
     const content::NotificationDetails& details) {
-  content::Details<const extensions::Extension> extension(details);
+  const extensions::Extension* extension =
+      content::Details<const extensions::InstalledExtensionInfo>(details)->
+          extension;
   GURL app_origin =
       extensions::Extension::GetBaseURLFromExtensionId(extension->id());
   DVLOG(1) << "Handle extension notification for INSTALLED: " << app_origin;
   // NOTE: When an app is uninstalled and re-installed in a sequence,
   // |local_file_service_| may still keeps |app_origin| as disabled origin.
   local_file_service_->SetOriginEnabled(app_origin, true);
 }
 
 void SyncFileSystemService::HandleExtensionUnloaded(
     int type,
@@ skipping 67 matching lines @@
       syncer::APPS);
   remote_file_service_->SetSyncEnabled(sync_enabled_);
   if (sync_enabled_) {
     base::MessageLoopProxy::current()->PostTask(
         FROM_HERE, base::Bind(&SyncFileSystemService::MaybeStartSync,
                               AsWeakPtr()));
   }
 }
 
 }  // namespace sync_file_system