Current approach is to find breakpoint by the statement position that was used when setting breakpoint. This doesn't work when setting breakpoint by anything else but statement position.

(Question: could PC of existing breakpoint change, for example because of recompilation, or this approach is safe)

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/15685010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15021 ce2b1a6d-e550-0410-aec6-3dcde31c8c00