Backed out 1 changesets (bug 1478637) for browser_trackingUI_animation_2.js failures CLOSED TREE

Backed out changeset 85496f02e642 (bug 1478637)

browser/base/content/browser-contentblocking.js

@@ -379,18 +379,11 @@ var ContentBlocking = {
   },
 
   cancelAnimation() {
-    if (!this.iconBox.hasAttribute("animate")) {
-      return;
+    let iconAnimation = this.animatedIcon.getAnimations()[0];
+    if (iconAnimation && iconAnimation.currentTime) {
+      iconAnimation.cancel();
     }
-
-    window.promiseDocumentFlushed(() => {
-      return this.animatedIcon.getAnimations()[0];
-    }).then(iconAnimation => {
-      if (iconAnimation && iconAnimation.currentTime) {
-        iconAnimation.cancel();
-      }
-      this.iconBox.removeAttribute("animate");
-    });
+    this.iconBox.removeAttribute("animate");
   },
 
   onSecurityChange(state, webProgress, isSimulated) {