Make it possible to custom-paint without an Element.

sky/engine/core/painting/Picture.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_PICTURE_H_
+#define SKY_ENGINE_CORE_PAINTING_PICTURE_H_
+
+#include "sky/engine/platform/graphics/DisplayList.h"
+#include "sky/engine/tonic/dart_wrappable.h"
+#include "sky/engine/wtf/PassRefPtr.h"
+#include "sky/engine/wtf/RefCounted.h"
+
+namespace blink {
+
+class Picture : public RefCounted<Picture>, public DartWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    ~Picture() override;
+    static PassRefPtr<Picture> create(PassRefPtr<DisplayList>);
+
+    DisplayList* displayList() const { return m_displayList.get(); }
+
+private:
+    Picture(PassRefPtr<DisplayList>);
+
+    RefPtr<DisplayList> m_displayList;
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_PAINTING_PICTURE_H_