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

canvas_bench/sprites.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 sprites = (function() {
+  var objs;
+  var width;
+  var height;
+  var SPRITE_SPEED = 2;
+
+  var sprites = {};
+  sprites.init = function(w, h) {
+    objs = [];
+    width = w;
+    height = h;
+  };
+  sprites.add = function(img) {
+    var obj = { img: img,
+                  x: Math.random() * (width - img.width),
+                  y: Math.random() * (height - img.height),
+                 dx: SPRITE_SPEED * (Math.random() < .5 ? -1 : 1),
+                 dy: SPRITE_SPEED * (Math.random() < .5 ? -1 : 1) };
+    objs.push(obj);
+  };
+  sprites.draw = function(context) {
+    for (var i = 0, len = objs.length; i < len; ++i) {
+      var obj = objs[i];
+
+      obj.x += obj.dx;
+      if ((obj.x > (width - obj.img.width)) || (obj.x < 0))
+        obj.dx *= -1;
+
+      obj.y += obj.dy;
+      if ((obj.y > (height - obj.img.height)) || (obj.y < 0))
+        obj.dy *= -1;
+
+      context.drawImage(obj.img, obj.x, obj.y);
+  };
+  };
+  return sprites;
+})();