Media Galleries API: Fix MediaGalleriesPreferences finders race.

chrome/browser/media_galleries/media_file_system_registry.h

Index: chrome/browser/media_galleries/media_file_system_registry.h
diff --git a/chrome/browser/media_galleries/media_file_system_registry.h b/chrome/browser/media_galleries/media_file_system_registry.h
index 4c6b77716ed5b285632328819641dc7b7074563c..aacc435b7e504f9ea140fab5d7e09150d3bb123b 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.h
+++ b/chrome/browser/media_galleries/media_file_system_registry.h
@@ -76,13 +76,9 @@ class MediaFileSystemRegistry
       const extensions::Extension* extension,
       const MediaFileSystemsCallback& callback);
 
-  // Returns the initialized media galleries preferences for the specified
-  // |profile|. This method should be used instead of calling
-  // MediaGalleriesPreferences directly because this method also ensures that
-  // currently attached removable devices are added to the preferences.
-  // Called on the UI thread.
-  // Note: Caller must ensure that the storage monitor is initialized before
-  // calling this method.
+  // Returns the media galleries preferences for the specified |profile|.
+  // Called on the UI thread. Caller is responsible for ensuring that the
+  // preferences are initialized before use.
   MediaGalleriesPreferences* GetPreferences(Profile* profile);
 
   // RemovableStorageObserver implementation.
@@ -105,6 +101,11 @@ class MediaFileSystemRegistry
   typedef std::map<const base::FilePath::StringType, ScopedMTPDeviceMapEntry*>
       MTPDeviceDelegateMap;
 
+  void FinishGetMediaFileSystemsForExtension(
+      const content::RenderViewHost* rvh,
+      const extensions::Extension* extension,
+      const MediaFileSystemsCallback& callback);
+
   virtual void OnPermissionRemoved(MediaGalleriesPreferences* pref,
                                    const std::string& extension_id,
                                    MediaGalleryPrefId pref_id) OVERRIDE;
@@ -123,6 +124,8 @@ class MediaFileSystemRegistry
   void OnExtensionGalleriesHostEmpty(Profile* profile,
                                      const std::string& extension_id);
 
+  base::WeakPtrFactory<MediaFileSystemRegistry> weak_factory_;
+
   // Only accessed on the UI thread. This map owns all the
   // ExtensionGalleriesHost objects created.
   ExtensionGalleriesHostMap extension_hosts_map_;