Add APIs for dynamic display lists, using SkDrawable and SkPictureRecorder::endRecordingAsDrawable.

sky/engine/core/painting/Drawable.cpp

+// 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.
+
+#include "sky/engine/core/painting/Drawable.h"
+#include "sky/engine/core/painting/Picture.h"
+
+namespace blink {
+
+PassRefPtr<Drawable> Drawable::create(PassRefPtr<SkDrawable> skDrawable)
+{
+    ASSERT(skDrawable);
+    return adoptRef(new Drawable(skDrawable));
+}
+
+Drawable::Drawable(PassRefPtr<SkDrawable> skDrawable)
+    : m_drawable(skDrawable)
+{
+}
+
+PassRefPtr<Picture> Drawable::newPictureSnapshot()
+{
+    if (!m_drawable)
+        return nullptr;
+    return Picture::create(
+        adoptRef(m_drawable->newPictureSnapshot()));
+}
+
+Drawable::~Drawable()
+{
+}
+
+} // namespace blink