Adjust the font size of the text tracks to make them proportionally larger when switching to fullscreen mode

Signed-off-by: Greg Kraus <gdkraus@ncsu.edu>

src/js/tracks.js

@@ -143,6 +143,8 @@ vjs.TextTrack = function(player, options){
   this.activeCues_ = [];
   this.readyState_ = 0;
   this.mode_ = 0;
+  
+  this.player_.on('fullscreenchange', vjs.bind(this, this.adjustFontSize));
 };
 goog.inherits(vjs.TextTrack, vjs.Component);
 
@@ -301,6 +303,22 @@ vjs.TextTrack.prototype.mode = function(){
   return this.mode_;
 };
 
+/**
+ * Change the font size of the text track to make it larger when playing in fullscreen mode
+ * and restore it to its normal size when not in fullscreen mode.
+ */
+vjs.TextTrack.prototype.adjustFontSize = function(){
+    if (this.player_.isFullScreen) {
+        // Scale the font by the same factor as increasing the video width to the full screen window width.
+        // Additionally, multiply that factor by 1.4, which is the default font size for
+        // the caption track (from the CSS)
+        this.el_.style.fontSize = screen.width / this.player_.options_.width * 1.4 * 100 + '%';
+    } else {
+        // Change the font size of the text track back to its original non-fullscreen size
+        this.el_.style.fontSize = '';
+    }
+};
+
 /**
  * Create basic div to hold cue text
  * @return {Element}