Add Sky framework support for drawing images

R=abarth@chromium.org, abarth

Review URL: https://codereview.chromium.org/1151753009

examples/raw/spinning_image.dart

+// Copyright 2015 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.
+
+import 'dart:sky';
+
+double timeBase = null;
+
+Image image;
+
+void beginFrame(double timeStamp) {
+  if (timeBase == null) timeBase = timeStamp;
+  double delta = timeStamp - timeBase;
+  PictureRecorder canvas = new PictureRecorder(view.width, view.height);
+  canvas.translate(view.width / 2.0, view.height / 2.0);
+  canvas.rotateDegrees(delta / 10);
+  canvas.scale(0.2, 0.2);
+  Paint paint = new Paint()..setARGB(255, 0, 255, 0);
+  canvas.drawImage(image, -image.width / 2.0, -image.height / 2.0, paint);
+  view.picture = canvas.endRecording();
+  view.scheduleFrame();
+}
+
+void main() {
+  image = new Image();
+  image.src = "https://www.dartlang.org/logos/dart-logo.png";
+  view.setBeginFrameCallback(beginFrame);
+  view.scheduleFrame();
+}