ISSUE: WebCGMRect::union

union() is not a good method name. Given that 'union' is a C/C++
keyword, it cannot get compiled by the MIDL compiler (on Windows).
 
We need a new name. Either:
i) Union(): but we have so far, started method names using lower cap
characters.
ii) calcUnion() or getUnion(): or something similar.
 
Benoit.