This solves the problem that code runs very slow when the debugger is enabled.

BUG=v8:2179
TEST=

Review URL: https://chromiumcodereview.appspot.com/10544135

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11802 ce2b1a6d-e550-0410-aec6-3dcde31c8c00