Move detection of the range where weak references are found from the marking pass to the bitmap construction pass.
Move detection of the range where weak references are found from the marking pass to the bitmap construction pass.

git-svn-id: 98787b36aaefbae4b30fa755be920954cd25e1e4@1487 ae7d391e-3f74-4a2b-a0db-a8776840fd2a

dcjm/polyml,polyml/polyml,dcjm/polyml,mn200/polyml,polyml/polyml,polyml/polyml,dcjm/polyml,mn200/polyml,mn200/polyml,dcjm/polyml,mn200/polyml,polyml/polyml