Sky: Add a DrawLooper interface to the painting API to be used for shadows.

sky/engine/core/painting/LayerDrawLooperBuilder.h

+// 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.
+
+#ifndef SKY_ENGINE_CORE_PAINTING_LAYERDRAWLOOPERBUILDER_H_
+#define SKY_ENGINE_CORE_PAINTING_LAYERDRAWLOOPERBUILDER_H_
+
+#include "sky/engine/tonic/dart_wrappable.h"
+#include "sky/engine/wtf/PassRefPtr.h"
+#include "sky/engine/wtf/RefCounted.h"
+#include "third_party/skia/include/effects/SkLayerDrawLooper.h"
+
+namespace blink {
+
+class DrawLooper;
+class DrawLooperAddLayerCallback;
+class DrawLooperLayerInfo;
+
+class LayerDrawLooperBuilder : public RefCounted<LayerDrawLooperBuilder>,
+                               public DartWrappable {
+  DEFINE_WRAPPERTYPEINFO();
+ public:
+  ~LayerDrawLooperBuilder() override;
+  static PassRefPtr<LayerDrawLooperBuilder> create() {
+    return adoptRef(new LayerDrawLooperBuilder);
+  }
+
+  PassRefPtr<DrawLooper> build();
+  void addLayerOnTop(DrawLooperLayerInfo* layer_info,
+                     PassOwnPtr<DrawLooperAddLayerCallback>);
+
+ private:
+  LayerDrawLooperBuilder();
+
+  SkLayerDrawLooper::Builder draw_looper_builder_;
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_PAINTING_LAYERDRAWLOOPERBUILDER_H_