Add a simple compositor for Sky

sky/compositor/layer_client.h

+// Copyright 2014 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.
+
+#ifndef SKY_COMPOSITOR_LAYER_CLIENT_H_
+#define SKY_COMPOSITOR_LAYER_CLIENT_H_
+
+class SkCanvas;
+
+namespace gfx {
+class Rect;
+}
+
+namespace sky {
+
+class LayerClient {
+ public:
+  virtual void PaintContents(SkCanvas* canvas, const gfx::Rect& clip) = 0;
+
+ protected:
+  virtual ~LayerClient();
+};
+
+}  // namespace sky
+
+#endif  // SKY_COMPOSITOR_LAYER_CLIENT_H_