Using the ITextHost interface allows this notification to be received
for windowless richedit controls.  Windowed richedit conrols have an
ITextHost implementation that will fill in hwndFrom and idFrom, but
these should probably be initialized to 0 for windowless richedit
controls.

The situation the code tests for should never happen because either the
stateblock will still have a reference to the vertex declaration, or the
stateblock itself will be released.

It can only work with native user32 anyway.