Change the ColorFilter constructor to ColorFilter.Mode, in case we want to add

sky/engine/core/painting/ColorFilter.dart

Index: sky/engine/core/painting/ColorFilter.dart
diff --git a/sky/engine/core/painting/ColorFilter.dart b/sky/engine/core/painting/ColorFilter.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f7e261b18a5a7209434a0a677395fe56a20efedf
--- /dev/null
+++ b/sky/engine/core/painting/ColorFilter.dart
@@ -0,0 +1,13 @@
+// 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.
+
+part of dart.sky;
+
+/// Extends the generated _ColorFilter interface via the PrivateDart attribute.
+class ColorFilter extends _ColorFilter {
+  // This is the only ColorFilter type we need, but use a named constructor so
+  // we can add more in the future.
+  ColorFilter.Mode(Color color, TransferMode transferMode)
+      : super(color, transferMode) {}
+}