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

sky/engine/core/painting/DrawLooper.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_DRAWLOOPER_H_
+#define SKY_ENGINE_CORE_PAINTING_DRAWLOOPER_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/core/SkDrawLooper.h"
+
+namespace blink {
+
+class DrawLooper : public RefCounted<DrawLooper>, public DartWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    ~DrawLooper() override;
+    static PassRefPtr<DrawLooper> create(PassRefPtr<SkDrawLooper> looper)
+    {
+        return adoptRef(new DrawLooper(looper));
+    }
+
+    SkDrawLooper* looper()
+    {
+        return m_looper.get();
+    }
+private:
+    DrawLooper(PassRefPtr<SkDrawLooper> looper);
+
+    RefPtr<SkDrawLooper> m_looper;
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_PAINTING_DRAWLOOPER_H_