Reduce failsafe time for animation events. This makes the lock-time more consistent.

ui/webui/resources/js/util.js

Index: ui/webui/resources/js/util.js
diff --git a/ui/webui/resources/js/util.js b/ui/webui/resources/js/util.js
index 2707dbcdd25f12ec3d996f72d60fc049849293c5..7244a6341845b4658a040226cd2deef5c253c778 100644
--- a/ui/webui/resources/js/util.js
+++ b/ui/webui/resources/js/util.js
@@ -375,9 +375,18 @@ function createElementWithClassName(type, className) {
  * a timer and emulate the event if it is not fired when the timer expires.
  * @param {!HTMLElement} el The element to watch for webkitTransitionEnd.
  * @param {number} timeOut The maximum wait time in milliseconds for the
- *     webkitTransitionEnd to happen.
+ *     webkitTransitionEnd to happen. If not specified, it is fetched from |el|
+ *     using the transitionDuration style value.
  */
 function ensureTransitionEndEvent(el, timeOut) {

[xiyuan, 2016/03/18 15:37:48]

nit: timeOut -> opt_timeOut and update comments (jsdoc type and name)

i.e.
  @param {number=} opt_timeOut ...

[jdufault, 2016/03/18 17:31:56]

Done.

+  if (timeOut == null) {

[xiyuan, 2016/03/18 15:37:48]

"=== undefined" to test whether an optional arg is passed in,

i.e.
  if (timeOut === undefined) {

[jdufault, 2016/03/18 17:31:56]

Done.

+    var style = getComputedStyle(el);
+    timeOut = parseFloat(style.transitionDuration) * 1000;
+
+    // Give an additional 50ms buffer for the animation to complete.
+    timeOut += 50;
+  }
+
   var fired = false;
   el.addEventListener('webkitTransitionEnd', function f(e) {
     el.removeEventListener('webkitTransitionEnd', f);