Bug 1420488 - part2 : add test. r=jwwang

MozReview-Commit-ID: 1clhH9B2mIf

--HG--
extra : rebase_source : 03da182dfdcba08919a7b0f77adc697ded6b50a6

toolkit/content/tests/browser/browser.ini

@@ -19,6 +19,7 @@ support-files =
   file_redirect_to.html
   file_silentAudioTrack.html
   file_webAudio.html
+  gizmo.mp4
   head.js
   image.jpg
   image_page.html
@@ -30,6 +31,7 @@ support-files =
 tags = audiochannel
 [browser_audioCompeting_onlyForActiveAgent.js]
 tags = audiochannel
+[browser_autoplay_policy_play_twice.js]
 [browser_autoscroll_disabled.js]
 [browser_block_autoplay_media.js]
 tags = audiochannel

toolkit/content/tests/browser/browser_autoplay_policy_play_twice.js

@@ -0,0 +1,48 @@
+const FILE = "https://example.com/browser/toolkit/content/tests/browser/gizmo.mp4";
+
+function setup_test_preference(enableUserGesture) {
+  let state = enableUserGesture ? "enable" : "disable";
+  info(`- set pref : ${state} user gesture -`);
+  return SpecialPowers.pushPrefEnv({"set": [
+    ["media.autoplay.enabled", false],
+    ["media.autoplay.enabled.user-gestures-needed", enableUserGesture]
+  ]});
+}
+
+async function allow_play_for_played_video() {
+  info("- open new tab  -");
+  let tab = await BrowserTestUtils.openNewForegroundTab(window.gBrowser,
+                                                        "about:blank");
+  info("- create video -");
+  let document = tab.linkedBrowser.contentDocument;
+  let video = document.createElement("video");
+  video.src = FILE;
+  video.controls = true;
+  document.body.appendChild(video);
+
+  info("- simulate user-click to start video -");
+  let waitForPlayEvent = once(video, "play");
+  await BrowserTestUtils.synthesizeMouseAtCenter(video, {button: 0},
+                                                 tab.linkedBrowser);
+  info("- video starts playing -");
+  await waitForPlayEvent;
+
+  info("- call video play() again -");
+  try {
+    await video.play();
+    ok(true, "success to resolve play promise");
+  } catch (e) {
+    ok(false, "promise should not be rejected");
+  }
+
+  info("- remove tab -");
+  await BrowserTestUtils.removeTab(tab);
+}
+
+add_task(async function start_test() {
+  await setup_test_preference(true);
+  await allow_play_for_played_video();
+
+  await setup_test_preference(false);
+  await allow_play_for_played_video();
+});

toolkit/content/tests/browser/head.js

@@ -212,3 +212,15 @@ class DateTimeTestHelper {
     this.panel = null;
   }
 }
+
+/**
+ * Used to listen events if you just need it once
+ */
+function once(target, name) {
+  var p = new Promise(function(resolve, reject) {
+    target.addEventListener(name, function() {
+      resolve();
+    }, {once: true});
+  });
+  return p;
+}