Make it possible to custom-paint without an Element.

sky/engine/core/painting/Picture.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/config.h"
+#include "sky/engine/core/painting/Picture.h"
+
+#include "base/logging.h"
+
+namespace blink {
+
+PassRefPtr<Picture> Picture::create(PassRefPtr<DisplayList> list)
+{
+    ASSERT(list);
+    return adoptRef(new Picture(list));
+}
+
+Picture::Picture(PassRefPtr<DisplayList> list)
+    : m_displayList(list)
+{
+}
+
+Picture::~Picture()
+{
+}
+
+} // namespace blink