Expose APIs for text track settings

Source/core/css/mediaControls.css

 /*
  * Copyright (C) 2009 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 330 matching lines @@
 audio::-webkit-media-controls-fullscreen-volume-max-button, video::-webkit-media-controls-fullscreen-volume-max-button {
     display: none;
 }
 
 video::-webkit-media-text-track-container {
     position: relative;
     width: 100%;
     overflow: hidden;
     padding-bottom: 5px;
 
-    font: 22px sans-serif;
+    font-family: sans-serif;

[srivats, 2015/03/26 01:36:02]

I reverted this back because this change broke the test:
media/track/track-cue-rendering-on-resize.html

     text-align: center;
     color: rgba(255, 255, 255, 1);
 
     letter-spacing: normal;
     word-spacing: normal;
     text-transform: none;
     text-indent: 0;
     text-decoration: none;
     pointer-events: none;
     -webkit-user-select: none;
@@ skipping 49 matching lines @@
     font-weight: bold;
 }
 
 video::-webkit-media-text-track-container u {
     text-decoration: underline;
 }
 
 video::-webkit-media-text-track-container i {
     font-style: italic;
 }