Clear baseRenderStyle on detach.

Source/core/animation/ActiveAnimations.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 94 matching lines @@
         m_baseRenderStyle = nullptr;
         return;
     }
 #if ENABLE(ASSERT)
     if (m_baseRenderStyle && renderStyle)
         ASSERT(*m_baseRenderStyle == *renderStyle);
 #endif
     m_baseRenderStyle = RenderStyle::clone(renderStyle);
 }
 
+void ActiveAnimations::clearBaseRenderStyle()
+{
+    m_baseRenderStyle = nullptr;
+}
+
 } // namespace blink