Unprefix usage of -webkit-transform in tests

LayoutTests/compositing/squashing/abspos-under-abspos-overflow-scroll.html

 <style type="text/css">
   .first {
     height:400px;
     background-color: red;
-    -webkit-transform: translateZ(0);
+    transform: translateZ(0);
   }
 
   .second {
     left: 100px;
     bottom: 0px; 
     background-color:blue;
     width:7px;
     height:562px;
-    position: absolute; -webkit-transform: translateX(0)
+    position: absolute; transform: translateX(0)
   }
 
   .outer {
     overflow: scroll;
     /* FIXME: make this height: 500px to expose another bug */
     height: 600px;
     width: 500px;
     position: absolute;
     bottom:10px;
     background-color: grey;
   }
 </style>
 <div class="outer">
   <div class="first"> </div>
   <div class="second"> </div>
 </div>
 <script>
     if (window.internals)
         window.internals.settings.setLayerSquashingEnabled(true);
 </script>