Gallery: Add support for Media Keys

ui/file_manager/gallery/js/slide_mode.js

Index: ui/file_manager/gallery/js/slide_mode.js
diff --git a/ui/file_manager/gallery/js/slide_mode.js b/ui/file_manager/gallery/js/slide_mode.js
index d0c04b662a8e3ba47aeb98a7d232c4a87d8585a9..ba445f03b893a1a404d174197a214c9f5d182614 100644
--- a/ui/file_manager/gallery/js/slide_mode.js
+++ b/ui/file_manager/gallery/js/slide_mode.js
@@ -607,7 +607,10 @@ SlideMode.prototype.getNextSelectedIndex_ = function(direction) {
  * @param {string} keyID Key identifier.
  */
 SlideMode.prototype.advanceWithKeyboard = function(keyID) {
-  this.advanceManually(keyID === 'Up' || keyID === 'Left' ? -1 : 1);
+  var prev = (keyID === 'Up' ||
+              keyID === 'Left' ||
+              keyID === 'MediaPreviousTrack');
+  this.advanceManually(prev ? -1 : 1);
 };
 
 /**
@@ -806,10 +809,12 @@ SlideMode.prototype.onKeyDown = function(event) {
   if (this.isSlideshowOn_()) {
     switch (keyID) {
       case 'U+001B':  // Escape exits the slideshow.
+      case 'MediaStop':
         this.stopSlideshow_(event);
         break;
 
       case 'U+0020':  // Space pauses/resumes the slideshow.
+      case 'MediaPlayPause':
         this.toggleSlideshowPause_();
         break;
 
@@ -817,6 +822,8 @@ SlideMode.prototype.onKeyDown = function(event) {
       case 'Down':
       case 'Left':
       case 'Right':
+      case 'MediaNextTrack':
+      case 'MediaPreviousTrack':
         this.advanceWithKeyboard(keyID);
         break;
     }
@@ -853,6 +860,8 @@ SlideMode.prototype.onKeyDown = function(event) {
     case 'Down':
     case 'Left':
     case 'Right':
+    case 'MediaNextTrack':
+    case 'MediaPreviousTrack':
       this.advanceWithKeyboard(keyID);
       break;