Added framework for canvas benchmark and two examples that stress drawImage. One example draws mult…

canvas_bench/bench.js

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var bench = (function() {
+  var rafFunc;
+  var drawFunc;
+  
+  function tick() {
+    drawFunc();
+    rafFunc(tick);
+  };
+
+  function startAnimation() {
+    rafFunc = window.requestAnimationFrame ||
+              window.webkitRequestAnimationFrame ||
+              window.mozRequestAnimationFrame ||
+              window.oRequestAnimationFrame ||
+              window.msRequestAnimationFrame;
+    rafFunc(tick);
+  };
+
+  var bench = {};
+  bench.run = function(df) {
+    drawFunc = df;
+    startAnimation();
+  };
+  return bench;
+})();