Animations: Make perf tests for web animations animate properly.

PerformanceTests/Animation/api-balls-keyframe-animations.html

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 Copyright (c) 2012 Cameron Adams. All rights reserved.
 Copyright (c) 2012 Code Aurora Forum. All rights reserved.
 Copyright (C) 2013 Google Inc. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
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     * Redistributions of source code must retain the above copyright
 notice, this list of conditions and the following disclaimer.
@@ skipping 59 matching lines @@
 var particles = [];
 var allParticleKeyframes = [];
 
 window.onload = function () {
     PerfTestRunner.prepareToMeasureValuesAsync({done: onCompletedRun, unit: 'fps'});
 
     // Create the particles
     for (var i = 0; i < maxParticles; i++) {
         generateParticleKeyframes(i);
         var particle = new Particle(i);
+        particle.start();
         particles.push(particle);
     }
-    for (var i = 0; i < maxParticles; i++)
-        particles[i].start();
 
     startTrackingFrameRate();
 }
 
 function generateParticleKeyframes(index) {
     allParticleKeyframes[index] = [];
 
     var angle = Math.PI * 2 * PerfTestRunner.random();
     var velocity = minVelocity + ((maxVelocity - minVelocity) * PerfTestRunner.random());
     var x = stageWidth / 2 - particleRadius;
@@ skipping 32 matching lines @@
             y += dy * dt;
         } else {
             t += collision.dt;
             x = collision.x;
             y = collision.y;
             dx = collision.dx;
             dy = collision.dy;
         }
         allParticleKeyframes[index].push(generateKeyframe(t, x, y));
     }
-
-    return keyframes;
 }
 
 function generateKeyframe(t, x, y) {
     return {left: x + "px", top: y + "px", offset: t / animationDuration };
 }
 
 function Particle(index)
 {
     // Create visual element for the particle.
     var domNode = document.createElement('span');
     document.body.appendChild(domNode);
 
     // Set colour of element.
     domNode.style.backgroundColor = colors[Math.floor(Math.random() * colors.length)];
 
     function start() {
-        var player = domNode.animate(allParticleKeyframes[index], {easing: "linear", iterations: Infinity, direction: "alternate", duration: animationDuration});
+        var player = domNode.animate(allParticleKeyframes[index], {easing: "linear", iterations: Infinity, direction: "alternate", duration: animationDuration * 1000});
     }
 
     function destroy()
     {
         document.body.removeChild(domNode);
     }
 
     this.start = start;
     this.destroy = destroy;
 }
 
 function onCompletedRun() {
     testRunning = false;
     stopTrackingFrameRate();
 
     for (var i = 0; i < particles.length; i++)
         particles[i].destroy();
     particles = [];
 }
 </script>
 <style id="keyframes"></style>
 </head>
 </html>