Refactor touch hit-testing hover/active tests.

LayoutTests/fast/events/touch/gesture/resources/gesture-tap-active-state-iframe-inner.html

 <!DOCTYPE html>
 <html>
+<link rel="stylesheet" href="../../resources/touch-hover-active-tests.css">
 <style type="text/css">
 #box {
     position: absolute;
-    background-color: blue;
     width: 300px;
     height: 100px;
     top: 100px;
 }
-
-#box:active {
-    background-color: red;
-}
-
 </style>
-<script>
-var color;
-function isBoxActive()
-{
-    // These need to match the background-color used above, after round-tripping.
-    var defaultColor = "rgb(0, 0, 255)";
-    var activeColor = "rgb(255, 0, 0)";
-
-    var b = document.getElementById('box');
-    color = getComputedStyle(b).backgroundColor;
-    if (color == activeColor)
-      return true;
-    if (color != defaultColor)
-      throw "Got unexpected backgroundColor: " + color;
-    return false;
-}
-
-</script>
-<body onload='parent.runTests(isBoxActive)'>
-<div id='box'>Gestures go here</div>
+<body>
+<div id='box' class='touch-interactive'>Gestures go here</div>
 </body>
 </html>