Reduce usage of webkit prefixes in extension examples

chrome/common/extensions/docs/templates/articles/sencha_framework.html

 <meta name="doc-family" content="apps">
 <h1>Build Apps with Sencha Ext JS</h1>
 
 <p>
 The goal of this doc is to get you started
 on building Chrome Apps with the
 <a href="http://www.sencha.com/products/extjs">Sencha Ext JS</a> framework.
 To achieve this goal,
 we will dive into a media player app built by Sencha.
 The <a href="https://github.com/GoogleChrome/sencha-video-player-app">source code</a>
@@ skipping 463 matching lines @@
 
     var animEnd = function(e) {
 
         //show body el
         mediaBody.style.display = '';
 
         //play media
         mediaEl.play();
 
         //clear listeners
-        playerCt.removeEventListener( 'webkitTransitionEnd', animEnd, false );
+        playerCt.removeEventListener( 'transitionend', animEnd, false );
         animEnd = null;
     };
 
     //load media
     mediaEl.src = url;
     mediaEl.load();
 
     //animate in player
-    playerCt.addEventListener( 'webkitTransitionEnd', animEnd, false );
-    playerCt.style.webkitTransform = "translateY(0)";
+    playerCt.addEventListener( 'transitionend', animEnd, false );
+    playerCt.style.transform = "translateY(0)";
 
     //reply postmessage
     data.result = true;
     sendMessage(data);
 }
 </pre>
 
 <h2 id="seven">Save media offline</h2>
 
 <p>
@@ skipping 64 matching lines @@
     }
 );
 </pre>
 
 <p>
 When the download process is finished,
 <code>MediaExplorer</code> updates the media file list and the media player tree panel.
 </p>
 
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