Bug 1195180 part 9 - Add test for seeking finished -> paused; r=heycam

This patch adds a test that even when we seek from being irrelevant to another
state where we no longer need ticks that we still spin the refresh driver
in order to queue and dispatch an animationstart event.

dom/animation/test/css-animations/file_animation-currenttime.html

@@ -441,6 +441,24 @@ async_test(function(t) {
   animation.currentTime = currentTimeForAfterPhase(animation.timeline);
 }, 'Redundant change, after -> active, then back');
 
+async_test(function(t) {
+  var div = addDiv(t, {'class': 'animated-div'});
+  var eventWatcher = new EventWatcher(t, div, CSS_ANIM_EVENTS);
+  div.style.animation = ANIM_PROPERTY_VAL;
+  var animation = div.getAnimations()[0];
+
+  animation.pause();
+  animation.currentTime = currentTimeForAfterPhase(animation.timeline);
+
+  eventWatcher.wait_for(['animationstart',
+                         'animationend']).then(t.step_func(function() {
+    animation.currentTime = currentTimeForActivePhase(animation.timeline);
+    return eventWatcher.wait_for('animationstart');
+  })).then(t.step_func(function() {
+    t.done();
+  }));
+
+}, 'Seeking finished -> paused dispatches animationstart');
 
 async_test(function(t) {
   var div = addDiv(t, {'class': 'animated-div'});