Make it possible to custom-paint without an Element.

sky/engine/core/painting/PictureRecorder.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_PICTURERECORDER_H_
+#define SKY_ENGINE_CORE_PAINTING_PICTURERECORDER_H_
+
+#include "sky/engine/core/painting/Canvas.h"
+
+namespace blink {
+
+class Picture;
+
+class PictureRecorder : public Canvas {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    ~PictureRecorder() override;
+    static PassRefPtr<PictureRecorder> create(double width, double height);
+
+    PassRefPtr<Picture> endRecording();
+
+private:
+    PictureRecorder(const FloatSize& size);
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_PAINTING_PICTURERECORDER_H_