Store unload promise on player

CONTRIBUTORS

@@ -24,6 +24,7 @@
 
 Andy Hochhaus <[email protected]>
 Chad Assareh <[email protected]>
+Chris Fillmore <[email protected]>
 Costel Madalin Grecu <[email protected]>
 Donato Borrello <[email protected]>
 Esteban Dosztal <[email protected]>

lib/player.js

@@ -88,6 +88,9 @@ shaka.Player = function(video, opt_dependencyInjector) {
   /** @private {Promise} */
   this.mediaSourceOpen_ = null;
 
+  /** @private {Promise} */
+  this.unloadPromise_ = null;
+
   /** @private {shaka.media.Playhead} */
   this.playhead_ = null;
 
@@ -378,14 +381,14 @@ shaka.Player.probeSupport = function() {
  */
 shaka.Player.prototype.load = function(manifestUri, opt_startTime,
                                        opt_manifestParserFactory) {
-  var unloadPromise = this.unload();
+  this.unload();
   var loadChain = new shaka.util.CancelableChain();
   this.loadChain_ = loadChain;
   this.dispatchEvent(new shaka.util.FakeEvent('loading'));
 
   return loadChain.then(function() {
-    return unloadPromise;
-  }).then(function() {
+    return this.unloadPromise_;
+  }.bind(this)).then(function() {
 
     goog.asserts.assert(this.networkingEngine_, 'Must not be destroyed');
     return shaka.media.ManifestParser.getFactory(
@@ -753,24 +756,49 @@ shaka.Player.prototype.isBuffering = function() {
  * @export
  */
 shaka.Player.prototype.unload = function() {
-  if (this.destroyed_) return Promise.resolve();
+  if (this.unloadPromise_) {
+    // An unload is currently in progress. Do not initiate another one.
+    return this.unloadPromise_;
+  }
+
+  if (this.destroyed_) {
+    // No unloading necessary.
+    return Promise.resolve();
+  }
+
   this.dispatchEvent(new shaka.util.FakeEvent('unloading'));
 
   if (this.loadChain_) {
     // A load is in progress.  Cancel it, then reset the streaming system.
     var interrupt = new shaka.util.Error(
         shaka.util.Error.Category.PLAYER,
         shaka.util.Error.Code.LOAD_INTERRUPTED);
-    return this.loadChain_.cancel(interrupt)
-        .then(this.resetStreaming_.bind(this));
+    return this.createUnloadPromise_(this.loadChain_.cancel(interrupt)
+        .then(this.resetStreaming_.bind(this)));
   } else {
-    // No loads or unloads are in progress.
-    // Just reset the streaming system if needed.
-    return this.resetStreaming_();
+    // No loads are in progress. Just reset the streaming system if needed.
+    return this.createUnloadPromise_(this.resetStreaming_());
   }
 };
 
 
+/**
+ * Create an unload promise and store it on the player until unloading
+ * is complete.
+ * @private
+ * @param {!Promise} unloadProcess Unloading steps to perform before destroying
+ *     the unload promise.
+ * @return {!Promise}
+ */
+shaka.Player.prototype.createUnloadPromise_ = function(unloadProcess) {
+  this.unloadPromise_ = unloadProcess.then(function() {
+    this.unloadPromise_ = null;
+  }.bind(this));
+
+  return this.unloadPromise_;
+};
+
+
 /**
  * Gets the current effective playback rate.  If using trick play, it will
  * return the current trick play rate; otherwise, it will return the video