Bug 1623962 - ensure to close PIP window before removing its belonging tab r=jya

This patch will do :
- close PIP window before remove the tab which PIP window belongs to

The advantage of doing so :
- avoid hitting the error which was caused by closing PIP window too late

Differential Revision: https://phabricator.services.mozilla.com/D72987

dom/media/mediacontrol/tests/browser_media_control_main_controller.js

@@ -132,7 +132,7 @@ add_task(async function testPIPControllerIsAlwaysMainController() {
   await isCurrentMetadataEqualTo(tab0.metadata);
 
   info(`trigger Picture-in-Picture mode for tab0`);
-  await triggerPictureInPicture(tab0.linkedBrowser, testVideoId);
+  const winPIP = await triggerPictureInPicture(tab0.linkedBrowser, testVideoId);
 
   info(`start media for tab1, main controller should still be tab0`);
   await playMediaAndWaitUntilRegisteringController(tab1, testVideoId);
@@ -141,6 +141,7 @@ add_task(async function testPIPControllerIsAlwaysMainController() {
   await isCurrentMetadataEqualTo(tab0.metadata);
 
   info(`remove tab0 and wait until main controller changes`);
+  await BrowserTestUtils.closeWindow(winPIP);
   await Promise.all([
     waitUntilMainMediaControllerChanged(),
     BrowserTestUtils.removeTab(tab0),

dom/media/mediacontrol/tests/browser_media_control_stop_timer.js

@@ -52,7 +52,7 @@ add_task(async function testNotToStopMediaControlForPIPVideo() {
   await playMedia(tab, testVideoId);
 
   info(`trigger PIP mode`);
-  await triggerPictureInPicture(tab.linkedBrowser, testVideoId);
+  const winPIP = await triggerPictureInPicture(tab.linkedBrowser, testVideoId);
 
   info(`pause media and the stop timer would not stop media control`);
   await pauseMedia(tab, testVideoId);
@@ -62,6 +62,7 @@ add_task(async function testNotToStopMediaControlForPIPVideo() {
   await checkOrWaitUntilMediaStartedPlaying(tab, testVideoId);
 
   info(`remove tab`);
+  await BrowserTestUtils.closeWindow(winPIP);
   await BrowserTestUtils.removeTab(tab);
 });