Will add a chrome-browser test to ensure the play() can start or fail on different user-gestures scenario.

Comment on attachment 8932724 [details] Bug 1421518 - add user-gestures test for the autoplay policy. https://reviewboard.mozilla.org/r/203774/#review210432 ::: toolkit/content/tests/browser/browser_autoplay_policy_user_gestures.js:59 (Diff revision 2) > + info("- can't autoplay without user activation -"); > + await canplayPromise; > + ok(video.paused, "video can't start without user input."); > + > + info("- call play() without user activation -"); > + await video.play().catch(function() { You don't need 'await' if you want to call .then() or .catch() on a promise. ::: toolkit/content/tests/browser/browser_autoplay_policy_user_gestures.js:84 (Diff revision 2) > + info("- can't autoplay without user activation -"); > + await canplayPromise; > + ok(video.paused, "video can't start without user input."); > + > + info("- call play() without user activation -"); > + await video.play().catch(function() { This test is already done in test_play_without_user_gesture(). You don't need to duplicate the test here.

Comment on attachment 8932724 [details] Bug 1421518 - add user-gestures test for the autoplay policy. https://reviewboard.mozilla.org/r/203774/#review210450 ::: toolkit/content/tests/browser/browser_autoplay_policy_user_gestures.js:59 (Diff revision 2) > + info("- can't autoplay without user activation -"); > + await canplayPromise; > + ok(video.paused, "video can't start without user input."); > + > + info("- call play() without user activation -"); > + await video.play().catch(function() { That awit is used to keep the code running in correct sequence. If you remove it, the catch might be executed after removeTab().

Pushed by alwu@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/213ae1ab70d4 add user-gestures test for the autoplay policy. r=jwwang