Web Animations CSS: Fix crash when transitioning background or mask properties

Source/core/rendering/style/StyleBackgroundData.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 10 matching lines @@
 
 #include "config.h"
 #include "core/rendering/style/StyleBackgroundData.h"
 
 #include "core/rendering/style/RenderStyle.h"
 #include "core/rendering/style/RenderStyleConstants.h"
 
 namespace WebCore {
 
 StyleBackgroundData::StyleBackgroundData()
-    : m_background(BackgroundFillLayer)
+    : m_background(BackgroundFillLayer, true)
     , m_color(RenderStyle::initialBackgroundColor())
 {
 }
 
 StyleBackgroundData::StyleBackgroundData(const StyleBackgroundData& o)
     : RefCounted<StyleBackgroundData>()
     , m_background(o.m_background)
     , m_color(o.m_color)
     , m_outline(o.m_outline)
 {
 }
 
 bool StyleBackgroundData::operator==(const StyleBackgroundData& o) const
 {
     return m_background == o.m_background && m_color == o.m_color && m_outline == o.m_outline;
 }
 
 } // namespace WebCore