Gallery.app: Decrease toolbar hiding timeout seconds.

BUG=421840
TEST=manually

Review URL: https://codereview.chromium.org/644883002

Cr-Commit-Position: refs/heads/master@{#299053}

ui/file_manager/gallery/js/gallery.js

@@ -237,7 +237,7 @@ Gallery.prototype.__proto__ = cr.EventTarget.prototype;
  * @const
  * @type {number}
  */
-Gallery.FADE_TIMEOUT = 3000;
+Gallery.FADE_TIMEOUT = 2000;
 
 /**
  * First time tools fade-out timeout in milliseconds.