Add support for maat in Firefox 49 (#852)

* use window.isSecureContext to detect ff 49

* fix tests

* fix linting

* make supportsAudioInfoChange private

* forgot to save this file before commit

* detect firefox 49 by user agent parsing for version number

@@ -18,8 +18,6 @@ Maintenance Status: Stable
   - [Manual Build](#manual-build)
 - [Contributing](#contributing)
 - [Getting Started](#getting-started)
-- [Known Issues](#known-issues)
-  - [IE11](#ie11)
 - [Documentation](#documentation)
   - [Options](#options)
     - [How to use](#how-to-use)
@@ -43,6 +41,9 @@ Maintenance Status: Stable
     - [mediachange](#mediachange)
   - [In-Band Metadata](#in-band-metadata)
 - [Hosting Considerations](#hosting-considerations)
+- [Known Issues](#known-issues)
+  - [IE11](#ie11)
+  - [Fragmented MP4 Support](#fragmented-mp4-support)
   - [Testing](#testing)
 - [Release History](#release-history)
 - [Building](#building)

@@ -382,7 +382,7 @@ export class MasterPlaylistController extends videojs.EventTarget {
   }
 
   handleAudioinfoUpdate_(event) {
-    if (!videojs.browser.IS_FIREFOX ||
+    if (Hls.supportsAudioInfoChange_() ||
         !this.audioInfo_ ||
         !objectChanged(this.audioInfo_, event.info)) {
       this.audioInfo_ = event.info;
@@ -391,7 +391,7 @@ export class MasterPlaylistController extends videojs.EventTarget {
 
     let error = 'had different audio properties (channels, sample rate, etc.) ' +
         'or changed in some other way.  This behavior is currently ' +
-        'unsupported in Firefox due to an issue: \n\n' +
+        'unsupported in Firefox 48 and below due to an issue: \n\n' +
         'https://bugzilla.mozilla.org/show_bug.cgi?id=1247138\n\n';
 
     let enabledIndex =

@@ -244,6 +244,26 @@ Hls.isSupported = function() {
                           'your player\'s techOrder.');
 };
 
+const USER_AGENT = window.navigator && window.navigator.userAgent || '';
+
+/**
+ * Determines whether the browser supports a change in the audio configuration
+ * during playback. Currently only Firefox 48 and below do not support this.
+ * window.isSecureContext is a propterty that was added to window in firefox 49,
+ * so we can use it to detect Firefox 49+.
+ *
+ * @return {Boolean} Whether the browser supports audio config change during playback
+ */
+Hls.supportsAudioInfoChange_ = function() {
+  if (videojs.browser.IS_FIREFOX) {
+    let firefoxVersionMap = (/Firefox\/([\d.]+)/i).exec(USER_AGENT);
+    let version = parseInt(firefoxVersionMap[1], 10);
+
+    return version >= 49;
+  }
+  return true;
+};
+
 const Component = videojs.getComponent('Component');
 
 /**

@@ -421,9 +421,14 @@ function() {
   QUnit.equal(this.player.tech_.hls.stats.bandwidth, 1, 'bandwidth we set above');
 });
 
-QUnit.test('blacklists the current playlist when audio changes in Firefox', function() {
+QUnit.test('blacklists the current playlist when audio changes in Firefox 48 & below',
+  function() {
     videojs.browser.IS_FIREFOX = true;
 
+    let origSupportsAudioInfoChange_ = videojs.Hls.supportsAudioInfoChange_;
+
+    videojs.Hls.supportsAudioInfoChange_ = () => false;
+
     // master
     standardXHRResponse(this.requests.shift());
     // media
@@ -447,7 +452,8 @@ QUnit.test('blacklists the current playlist when audio changes in Firefox', func
     QUnit.ok(media.excludeUntil > 0, 'blacklisted the old playlist');
     QUnit.equal(this.env.log.warn.callCount, 2, 'logged two warnings');
     this.env.log.warn.callCount = 0;
-});
+    videojs.Hls.supportsAudioInfoChange_ = origSupportsAudioInfoChange_;
+  });
 
 QUnit.test('updates the combined segment loader on media changes', function() {
   let updates = [];

@@ -1792,11 +1792,15 @@ QUnit.test('adds audio tracks if we have parsed some from a playlist', function(
   QUnit.equal(vjsAudioTracks[0].enabled, false, 'main track is disabled');
 });
 
-QUnit.test('when audioinfo changes on an independent audio track in Firefox, the enabled track is blacklisted and removed', function() {
+QUnit.test('when audioinfo changes on an independent audio track in Firefox 48 & below, the enabled track is blacklisted and removed', function() {
   let audioTracks = this.player.audioTracks();
   let oldLabel;
 
   videojs.browser.IS_FIREFOX = true;
+  let origSupportsAudioInfoChange_ = videojs.Hls.supportsAudioInfoChange_;
+
+  videojs.Hls.supportsAudioInfoChange_ = () => false;
+
   this.player.src({
     src: 'manifest/multipleAudioGroups.m3u8',
     type: 'application/vnd.apple.mpegurl'
@@ -1828,12 +1832,17 @@ QUnit.test('when audioinfo changes on an independent audio track in Firefox, the
   QUnit.notEqual(audioTracks[1].label, oldLabel, 'audio track at index 1 is not the same');
   QUnit.equal(defaultTrack.enabled, true, 'default track is enabled again');
   QUnit.equal(this.env.log.warn.calls, 1, 'firefox issue warning logged');
+  videojs.Hls.supportsAudioInfoChange_ = origSupportsAudioInfoChange_;
 });
 
-QUnit.test('audioinfo changes with one track, blacklist playlist', function() {
+QUnit.test('audioinfo changes with one track, blacklist playlist on Firefox 48 & below', function() {
   let audioTracks = this.player.audioTracks();
 
   videojs.browser.IS_FIREFOX = true;
+  let origSupportsAudioInfoChange_ = videojs.Hls.supportsAudioInfoChange_;
+
+  videojs.Hls.supportsAudioInfoChange_ = () => false;
+
   this.player.src({
     src: 'manifest/master.m3u8',
     type: 'application/vnd.apple.mpegurl'
@@ -1857,12 +1866,17 @@ QUnit.test('audioinfo changes with one track, blacklist playlist', function() {
   QUnit.equal(audioTracks.length, 1, 'still have one audio track');
   QUnit.ok(oldMedia.excludeUntil > 0, 'blacklisted old playlist');
   QUnit.equal(this.env.log.warn.calls, 2, 'firefox issue warning logged');
+  videojs.Hls.supportsAudioInfoChange_ = origSupportsAudioInfoChange_;
 });
 
 QUnit.test('changing audioinfo for muxed audio blacklists the current playlist in Firefox', function() {
   let audioTracks = this.player.audioTracks();
 
   videojs.browser.IS_FIREFOX = true;
+  let origSupportsAudioInfoChange_ = videojs.Hls.supportsAudioInfoChange_;
+
+  videojs.Hls.supportsAudioInfoChange_ = () => false;
+
   this.player.src({
     src: 'manifest/multipleAudioGroupsCombinedMain.m3u8',
     type: 'application/vnd.apple.mpegurl'
@@ -1910,6 +1924,7 @@ QUnit.test('changing audioinfo for muxed audio blacklists the current playlist i
   QUnit.equal(defaultTrack.enabled, true, 'default audio still enabled');
   QUnit.ok(oldPlaylist.excludeUntil > 0, 'blacklisted the old playlist');
   QUnit.equal(this.env.log.warn.calls, 2, 'firefox issue warning logged');
+  videojs.Hls.supportsAudioInfoChange_ = origSupportsAudioInfoChange_;
 });
 
 QUnit.test('cleans up the buffer when loading live segments', function() {