Bug 1525554 - Avoid testharness reporting error casued by unhandled rejected promises in media-source/mediasource-getvideoplaybackquality.html; r=annevk

Differential Revision: https://phabricator.services.mozilla.com/D32313

--HG--
extra : moz-landing-system : lando

testing/web-platform/tests/media-source/mediasource-getvideoplaybackquality.html

@@ -60,7 +60,7 @@
                   assert_false(sourceBuffer.updating, "updating");
                   mediaSource.endOfStream();
                   assert_less_than(mediaSource.duration, 10, "duration");
-                  mediaElement.play();
+                  mediaElement.play().catch(test.unreached_func("Unexpected promise rejection"));;
                   test.expectEvent(mediaElement, 'ended', 'mediaElement');
               });
 
@@ -103,7 +103,7 @@
                   mediaSource.endOfStream();
                   assert_less_than(mediaSource.duration, 10, "duration");
                   startTime = window.performance.now();
-                  mediaElement.play();
+                  mediaElement.play().catch(test.unreached_func("Unexpected promise rejection"));
                   test.expectEvent(mediaElement, 'ended', 'mediaElement');
               });