Added depth check to StepNextContinue. Do step out and queue actual StepNext if check failed.

R=yangguo@chromium.org,danno@chromium.org,vegorov@chromium.org
BUG=v8:1639
TEST=

Review URL: http://codereview.chromium.org/7780033
Patch from Fedor Indutny <fedor@indutny.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9264 ce2b1a6d-e550-0410-aec6-3dcde31c8c00