Rename 'video' to 'mediaElem'.

This emphasizes that both a <video> and <audio> elements can be used
in Shaka Player.

Closes #1555

Backported to v2.4.x

Change-Id: I2aa6e10b9ad7044588e1b418d938060aca333a2b

docs/tutorials/basic-usage.md

@@ -3,11 +3,11 @@
 Basic usage of Shaka Player is very easy:
 
 1. Start with {@tutorial welcome} and compile the library.
-2. Create a simple HTML page with a video element.
+2. Create a simple HTML page with a video or audio element.
 3. In your application's JavaScript:
   1. Install Shaka's polyfills.
   2. Check for browser support.
-  3. Create a Player object to wrap the video element.
+  3. Create a Player object to wrap the media element.
   4. Listen for errors.
   5. Load a manifest.
 

lib/player.js

@@ -47,8 +47,8 @@ goog.require('shaka.util.StreamUtils');
 /**
  * Construct a Player.
  *
- * @param {HTMLMediaElement=} video If provided, this is equivalent to calling
- *   attach(video, true) immediately after construction.
+ * @param {HTMLMediaElement=} mediaElem If provided, this is equivalent to
+ *   calling attach(mediaElem, true) immediately after construction.
  * @param {function(shaka.Player)=} opt_dependencyInjector Optional callback
  *   which is called to inject mocks into the Player.  Used for testing.
  *
@@ -58,7 +58,7 @@ goog.require('shaka.util.StreamUtils');
  * @extends {shaka.util.FakeEventTarget}
  * @export
  */
-shaka.Player = function(video, opt_dependencyInjector) {
+shaka.Player = function(mediaElem, opt_dependencyInjector) {
   shaka.util.FakeEventTarget.call(this);
 
   /** @private {boolean} */
@@ -182,8 +182,8 @@ shaka.Player = function(video, opt_dependencyInjector) {
 
   this.networkingEngine_ = this.createNetworkingEngine();
 
-  if (video) {
-    this.attach(video, true /* initializeMediaSource */);
+  if (mediaElem) {
+    this.attach(mediaElem, true /* initializeMediaSource */);
   }
 };
 goog.inherits(shaka.Player, shaka.util.FakeEventTarget);
@@ -493,7 +493,7 @@ shaka.Player.probeSupport = function() {
  * After calling attach, the media element is owned by the Player and should not
  * be used for other purposes until detach or destroy() are called.
  *
- * @param {!HTMLMediaElement} video
+ * @param {!HTMLMediaElement} mediaElem
  * @param {boolean=} initializeMediaSource If true, start initializing
  *   MediaSource right away.  This can improve load() latency for
  *   MediaSource-based playbacks.  Defaults to true.
@@ -505,7 +505,8 @@ shaka.Player.probeSupport = function() {
  *   media element.
  * @export
  */
-shaka.Player.prototype.attach = async function(video, initializeMediaSource) {
+shaka.Player.prototype.attach =
+    async function(mediaElem, initializeMediaSource) {
   if (initializeMediaSource === undefined) {
     initializeMediaSource = true;
   }
@@ -514,8 +515,8 @@ shaka.Player.prototype.attach = async function(video, initializeMediaSource) {
     await this.detach();
   }
 
-  this.video_ = video;
-  goog.asserts.assert(video, 'Cannot attach to a null media element!');
+  this.video_ = mediaElem;
+  goog.asserts.assert(mediaElem, 'Cannot attach to a null media element!');
 
   // Listen for video errors.
   this.eventManager_.listen(this.video_, 'error',