Make Chrome OS Audio Player survive page reload and OS restart.

chrome/browser/resources/file_manager/js/media/media_controls.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview MediaControls class implements media playback controls
  * that exist outside of the audio/video HTML element.
  */
 
 /**
@@ skipping 366 matching lines @@
     sliderContainer.classList.add('readonly');
 
   var valueToString = function(value) {
     return MediaControls.formatTime_(this.media_.duration * value);
   }.bind(this);
 
   this.duration_.textContent = valueToString(1);
 
   if (this.progressSlider_.setValueToStringFunction)
     this.progressSlider_.setValueToStringFunction(valueToString);
+
+  if (this.media_.seekable)
+    this.restorePlayState();
 };
 
 /**
  * 'timeupdate' event handler.
  * @private
  */
 MediaControls.prototype.onMediaProgress_ = function() {
   if (!this.media_.duration) {
     this.displayProgress_(0, 1);
     return;
@@ skipping 13 matching lines @@
   this.onPlayStateChanged();
 };
 
 /**
  * Called when the media playback is complete.
  */
 MediaControls.prototype.onMediaComplete = function() {};
 
 /**
  * Called when play/pause state is changed or on playback progress.
+ * This is the right moment to save the play state.
  */
 MediaControls.prototype.onPlayStateChanged = function() {};
 
 /**
+ * Restore play state. Base implementation is empty.
+ */
+MediaControls.prototype.restorePlayState = function() {};
+
+/**
+ * Encode current play/pause status and the current time into the page URL.
+ */
+MediaControls.prototype.encodeStateIntoLocation = function() {
+  if (!this.media_.duration)
+    return;
+
+  var playState = JSON.stringify({
+      play: this.isPlaying(),
+      time: this.media_.currentTime
+    });
+
+  var newLocation = document.location.origin + document.location.pathname +
+      document.location.search + '#' + playState;
+
+  history.replaceState(undefined, playState, newLocation);
+};
+
+/**
+ * Decode current play/pause status and the current time from the page URL.
+ * @return {boolean} True if decode succeeded.
+ */
+MediaControls.prototype.decodeStateFromLocation = function() {
+  var hash = document.location.hash.substring(1);
+  if (hash) {
+    try {
+      var playState = JSON.parse(hash);
+      if (!('time' in playState))
+        return false;
+
+      this.media_.currentTime = playState.time;
+
+      if (playState.play)
+        this.play();
+      else
+        this.pause();
+
+      return true;
+    } catch (e) {
+      console.warn('Cannot decode play state');
+    }
+  }
+  return false;
+};
+
+/**
  * Create a customized slider control.
  *
  * @param {HTMLElement} container The containing div element.
  * @param {number} value Initial value [0..1].
  * @param {number} range Number of distinct slider positions to be supported.
  * @param {function(number)} onChange Value change handler.
  * @param {function(boolean)} onDrag Drag begin/end handler.
  * @constructor
  */
 
@@ skipping 499 matching lines @@
     self.stateIcon_.setAttribute('visible', true);
     delay(function() {
       self.stateIcon_.setAttribute(
           'state', self.isPlaying() ? 'play' : 'pause');
       delay(hideStatusIcon, 1000);  /* Twice the animation duration. */
     });
   });
 };
 
 /**
- * 'durationchange' handler.
- * @private
- */
-VideoControls.prototype.onMediaDuration_ = function() {
-  MediaControls.prototype.onMediaDuration_.apply(this, arguments);
-  if (this.media_.duration && this.media_.seekable)
-    this.resumePosition();
-};
-
-/**
  * Toggle play/pause state.
  */
 VideoControls.prototype.togglePlayState = function() {
   if (this.isPlaying()) {
     // User gave the Pause command.
     this.savePosition();
   }
   MediaControls.prototype.togglePlayState.apply(this, arguments);
 };
 
@@ skipping 13 matching lines @@
     this.resumePositions_.removeValue(this.media_.src);
   } else {
     this.resumePositions_.setValue(this.media_.src, Math.floor(Math.max(0,
         this.media_.currentTime - VideoControls.RESUME_REWIND)));
   }
 };
 
 /**
  * Resume the playback position saved in the persistent storage.
  */
-VideoControls.prototype.resumePosition = function() {
+VideoControls.prototype.restorePlayState = function() {
   if (this.media_.duration >= VideoControls.RESUME_THRESHOLD) {
     var position = this.resumePositions_.getValue(this.media_.src);
     if (position)
       this.media_.currentTime = position;
   }
 };
 
 /**
  * Update style to best fit the size of the container.
  */
@@ skipping 177 matching lines @@
 AudioControls.prototype.onAdvanceClick_ = function(forward) {
   if (!forward &&
       (this.getMedia().currentTime > AudioControls.TRACK_RESTART_THRESHOLD)) {
     // We are far enough from the beginning of the current track.
     // Restart it instead of than skipping to the previous one.
     this.getMedia().currentTime = 0;
   } else {
     this.advanceTrack_(forward);
   }
 };