Media Galleries API: Fix MediaGalleriesPreferences finders race.

chrome/browser/media_galleries/fileapi/picasa_finder.h

Index: chrome/browser/media_galleries/fileapi/picasa_finder.h
diff --git a/chrome/browser/media_galleries/fileapi/picasa_finder.h b/chrome/browser/media_galleries/fileapi/picasa_finder.h
index 8b30597a04557c1db2b76882b960cab6c02a8400..c45d98aba22069c75f8573d8e19169bfc9620037 100644
--- a/chrome/browser/media_galleries/fileapi/picasa_finder.h
+++ b/chrome/browser/media_galleries/fileapi/picasa_finder.h
@@ -17,7 +17,8 @@ typedef base::Callback<void(const std::string&)> DeviceIDCallback;
 
 // Bounces to FILE thread to find Picasa database. If the platform supports
 // Picasa and a Picasa database is found, |callback| will be invoked on the
-// calling thread. Otherwise, |callback| is not invoked.
+// calling thread with the device ID. Otherwise, |callback| will be invoked
+// with an empty string.
 void FindPicasaDatabase(const DeviceIDCallback& callback);
 
 }