Polyfill video.play to silence confusing errors

Closes #836

Change-Id: Ie5b42bc707ce7443641e86c04ec116fd732bbbae

build/types/polyfill

@@ -9,5 +9,6 @@
 +../../lib/polyfill/patchedmediakeys_nop.js
 +../../lib/polyfill/patchedmediakeys_webkit.js
 +../../lib/polyfill/promise.js
++../../lib/polyfill/video_play_promise.js
 +../../lib/polyfill/videoplaybackquality.js
 +../../lib/polyfill/vttcue.js

lib/polyfill/video_play_promise.js

@@ -0,0 +1,59 @@
+/**
+ * @license
+ * Copyright 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+goog.provide('shaka.polyfill.VideoPlayPromise');
+
+goog.require('shaka.log');
+goog.require('shaka.polyfill.register');
+
+
+/**
+ * @namespace shaka.polyfill.VideoPlayPromise
+ *
+ * @summary A polyfill to silence the play() Promise in HTML5 video.
+ */
+
+
+/**
+ * Install the polyfill if needed.
+ */
+shaka.polyfill.VideoPlayPromise.install = function() {
+  shaka.log.debug('VideoPlayPromise.install');
+
+  if (window.HTMLMediaElement) {
+    var originalPlay = HTMLMediaElement.prototype.play;
+    HTMLMediaElement.prototype.play = function() {
+      var p = originalPlay.apply(this, arguments);
+      if (p) {
+        // This browser is returning a Promise from play().
+        // If the play() call fails or is interrupted, the Promise will be
+        // rejected.  Some apps, however, don't listen to this Promise,
+        // especially since it is not available cross-browser.  If the Promise
+        // is rejected without anyone listening for the failure, an error will
+        // appear in the JS console.
+        // To avoid confusion over this innocuous "error", we will install a
+        // catch handler on the Promise.  This does not prevent the app from
+        // also catching failures and handling them.  It only prevents the
+        // console message.
+        p.catch(function() {});
+      }
+      return p;
+    };
+  }
+};
+
+shaka.polyfill.register(shaka.polyfill.VideoPlayPromise.install);

shaka-player.uncompiled.js

@@ -49,6 +49,7 @@ goog.require('shaka.polyfill.MediaKeys');
 goog.require('shaka.polyfill.MediaSource');
 goog.require('shaka.polyfill.Promise');
 goog.require('shaka.polyfill.VTTCue');
+goog.require('shaka.polyfill.VideoPlayPromise');
 goog.require('shaka.polyfill.VideoPlaybackQuality');
 goog.require('shaka.polyfill.installAll');
 goog.require('shaka.util.Error');