The debugger exposes all native script which might include duplicates
having the same name. This is triggered by debug-script in stress mode
on the gc branch.

R=sgjesse@chromium.org
BUG=v8:1641
TEST=mjsunit/debug-script

Review URL: http://codereview.chromium.org/7740050

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9028 ce2b1a6d-e550-0410-aec6-3dcde31c8c00