plus a few other tweaks."

The problem with the original patch was that it did not take hidden
prototype objects into account in Runtime_GetPrototype.

R=kmillikin@chromium.org,rossberg@chromium.org
TEST=es5conform

Review URL: http://codereview.chromium.org/7056041

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8164 ce2b1a6d-e550-0410-aec6-3dcde31c8c00