shorten requestAnimationFrame test

src/support.js

@@ -13,7 +13,8 @@
 		a = div.getElementsByTagName("a")[0],
 		select = document.createElement("select"),
 		opt = select.appendChild( document.createElement("option") ),
-		input = div.getElementsByTagName("input")[0];
+		input = div.getElementsByTagName("input")[0],
+		raf = "RequestAnimationFrame";
 
 	// Can't get basic test support
 	if ( !all || !all.length || !a ) {
@@ -60,10 +61,9 @@
 
 		// Verify requestAnimationFrame mechanism existence
 		// use the prefixed name as the value
-		requestAnimationFrame: window.mozRequestAnimationFrame ?
-			'mozRequestAnimationFrame' :
-			window.webkitRequestAnimationFrame ?
-				'webkitRequestAnimationFrame' :
+		requestAnimationFrame:
+			window['moz' + raf] ? 'moz' + raf :
+			window['webkit' + raf] ? 'webkit' + raf :
 			false,
 
 		// Will be defined later