Revert of Enable gallery watches on Mac

chrome/browser/extensions/api/media_galleries_private/gallery_watch_state_tracker.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.
 
 // GalleryWatchStateTracker implementation.
 
 #include "chrome/browser/extensions/api/media_galleries_private/gallery_watch_state_tracker.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
@@ skipping 74 matching lines @@
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   MediaGalleriesPreferences* preferences =
       g_browser_process->media_file_system_registry()->GetPreferences(profile_);
   preferences->RemoveGalleryChangeObserver(this);
 }
 
 // static
 GalleryWatchStateTracker* GalleryWatchStateTracker::GetForProfile(
     Profile* profile) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+#if defined(OS_WIN) || defined(OS_LINUX)
+  // Gallery watch operation is not supported on Mac: crbug.com/144491.
   DCHECK(profile);
   MediaGalleriesPrivateAPI* private_api =
       MediaGalleriesPrivateAPI::Get(profile);
   // In unit tests, we don't have a MediaGalleriesPrivateAPI.
   if (private_api)
     return private_api->GetGalleryWatchStateTracker();
+#endif
   return NULL;
 }
 
 void GalleryWatchStateTracker::OnPermissionAdded(
     MediaGalleriesPreferences* preferences,
     const std::string& extension_id,
     MediaGalleryPrefId gallery_id) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   // Granted gallery permission.
   if (HasGalleryWatchInfo(extension_id, gallery_id, false))
@@ skipping 216 matching lines @@
     const std::string& extension_id,
     MediaGalleryPrefId gallery_id) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   if (HasGalleryWatchInfo(extension_id, gallery_id, true))
     return false;
   watched_extensions_map_[extension_id][gallery_id] = true;
   return true;
 }
 
 }  // namespace extensions