Added focus tracking to play/pause button. This fixes a bug where the tabbing, in certain condition, would get stuck on speed button.

common/lib/xmodule/xmodule/js/src/video/04_video_control.js

@@ -77,6 +77,11 @@ function () {
             state.el.on('mousemove', state.videoControl.showControls);
             state.el.on('keydown', state.videoControl.showControls);
         }
+        // The state.previousFocus is used in video_speed_control to track 
+        // the element that had the focus before it.
+        state.videoControl.playPauseEl.on('blur', function () {
+            state.previousFocus = 'playPause';
+        });
     }
 
     // ***************************************************************

common/lib/xmodule/xmodule/js/src/video/07_video_volume_control.js

@@ -126,7 +126,7 @@ function () {
                 // the volume clontrol.
                 state.volumeBlur = true;
                 // The following field is used in video_speed_control to track 
-                // the element that had the focus.
+                // the element that had the focus before it.
                 state.previousFocus = 'volume';
             });
     }

common/lib/xmodule/xmodule/js/src/video/08_video_speed_control.js

@@ -188,7 +188,7 @@ function () {
                     // If we are tabbing forward (previous focus is empty ie 
                     // play button), we open the dialog and set focus on the 
                     // first speed entry.
-                    if (state.previousFocus === '') {
+                    if (state.previousFocus === 'playPause') {
                         state.videoSpeedControl.el.addClass('open');
                         state.videoSpeedControl.videoSpeedsEl
                         .find('a.speed_link:first')
@@ -205,7 +205,6 @@ function () {
                         .focus();
                     }
                     
-                    state.previousFocus = '';
                 });