Add option to run ScopeIterator faster giving up nested scope chain.

We'd like to be able to trade nested scope chain info (consisting of with, block and catch scopes) in favor of speed in some cases.

BUG=chromium:340285
LOG=N
R=ulan@chromium.org, pfeldman, ulan, yangguo

Review URL: https://codereview.chromium.org/203463011

Patch from Andrey Adaykin <aandrey@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20162 ce2b1a6d-e550-0410-aec6-3dcde31c8c00