Bug 1489375 - part2 : add test. r=padenot

add test.

Differential Revision: https://phabricator.services.mozilla.com/D5800

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

toolkit/content/tests/browser/browser.ini

@@ -127,3 +127,5 @@ uses-unsafe-cpows = true
 [browser_sound_indicator_silent_video.js]
 tags = audiochannel
 [browser_resume_bkg_video_on_tab_hover.js]
+[browser_webAudio_hideSoundPlayingIcon.js]
+tags = audiochannel

toolkit/content/tests/browser/browser_webAudio_hideSoundPlayingIcon.js

@@ -0,0 +1,61 @@
+/**
+ * This test is used to ensure the 'sound-playing' icon would not disappear after
+ * sites call AudioContext.resume().
+ */
+"use strict";
+
+function setup_test_preference() {
+  return SpecialPowers.pushPrefEnv({"set": [
+    ["media.useAudioChannelService.testing", true],
+    ["browser.tabs.delayHidingAudioPlayingIconMS", 0],
+  ]});
+}
+
+function createAudioContext() {
+  content.ac = new content.AudioContext();
+  const ac = content.ac;
+  const dest = ac.destination;
+  const osc = ac.createOscillator();
+  osc.connect(dest);
+  osc.start();
+}
+
+async function resumeAudioContext() {
+  const ac = content.ac;
+  await ac.resume();
+  ok(true, "AudioContext is resumed.");
+}
+
+async function testResumeRunningAudioContext() {
+  info(`- create new tab -`);
+  const tab = await BrowserTestUtils.openNewForegroundTab(window.gBrowser,
+                                                          "about:blank");
+  const browser = tab.linkedBrowser;
+
+  info(`- create audio context -`);
+  // We want the same audio context to be used across different content
+  // tasks, so it needs to be loaded by a frame script.
+  const mm = tab.linkedBrowser.messageManager;
+  mm.loadFrameScript("data:,(" + createAudioContext.toString() + ")();", false);
+
+  info(`- wait for 'sound-playing' icon showing -`);
+  await waitForTabPlayingEvent(tab, true);
+
+  info(`- resume AudioContext -`);
+  await ContentTask.spawn(browser, null,
+                          resumeAudioContext);
+
+  info(`- 'sound-playing' icon should still exist -`);
+  await waitForTabPlayingEvent(tab, true);
+
+  info(`- remove tab -`);
+  await BrowserTestUtils.removeTab(tab);
+}
+
+add_task(async function start_test() {
+  info("- setup test preference -");
+  await setup_test_preference();
+
+  info("- start testing -");
+  await testResumeRunningAudioContext();
+});