Add an API to set the ColorFilter on a Paint object.

sky/examples/raw/shadow.dart

Index: sky/examples/raw/shadow.dart
diff --git a/sky/examples/raw/shadow.dart b/sky/examples/raw/shadow.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a83602e88d4dc0fbbd7634f656a7c042805f135b
--- /dev/null
+++ b/sky/examples/raw/shadow.dart
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+// 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';
+
+void beginFrame(double timeStamp) {
+  var size = 100.0;
+  PictureRecorder canvas = new PictureRecorder(view.width, view.height);
+  canvas.translate(size + 10.0, size + 10.0);
+
+  Paint paint = new Paint();
+  paint.setARGB(255, 0, 255, 0);
+  var builder = new LayerDrawLooperBuilder()
+    // Shadow layer.
+    ..addLayerOnTop(
+        new DrawLooperLayerInfo()..setOffset(5.0, 5.0)..setColorMode(5),
+        (Paint layerPaint) {
+      layerPaint.setARGB(128, 55, 55, 55);
+      // TODO(mpcomplete): add blur filter
+    })
+    // Main layer.
+    ..addLayerOnTop(new DrawLooperLayerInfo(), (Paint) {});
+  paint.setDrawLooper(builder.build());
+
+  canvas.drawPaint(new Paint()..setARGB(255, 255, 255, 255));
+  canvas.drawRect(new Rect.fromLTRB(-size, -size, size, size), paint);
+  view.picture = canvas.endRecording();
+}
+
+void main() {
+  view.setBeginFrameCallback(beginFrame);
+  view.scheduleFrame();
+}