Revert r13699 "Debugger: ScopeMirror has N^2 algorithm when building closure mirrors." because of WebKit crashes.

BUG=v8:2554
R=verwaest@chromium.org

Review URL: https://chromiumcodereview.appspot.com/12321108

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13714 ce2b1a6d-e550-0410-aec6-3dcde31c8c00