Disallow non-flexbox child renderers for RenderMedia

Source/core/rendering/RenderMedia.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 47 matching lines @@
 private:
     virtual RenderObjectChildList* virtualChildren() override final { return children(); }
     virtual const RenderObjectChildList* virtualChildren() const override final { return children(); }
 
     virtual LayerType layerTypeRequired() const override { return NormalLayer; }
 
     // FIXME: RenderMedia::layout makes assumptions about what children are allowed
     // so we can't support generated content.
     virtual bool canHaveGeneratedChildren() const override final { return false; }
     virtual bool canHaveChildren() const override final { return true; }
+    virtual bool isChildAllowed(RenderObject*, RenderStyle*) const override final;
 
     virtual const char* renderName() const override { return "RenderMedia"; }
     virtual bool isImage() const override final { return false; }
     virtual void paintReplaced(PaintInfo&, const LayoutPoint&) override;
 
     RenderObjectChildList m_children;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMedia, isMedia());
 
 } // namespace blink
 
 #endif // RenderMedia_h