Refactoring: Use fake cwd in release script tests.

TEST=script_test.py
R=tandrii@chromium.org
TBR=jarin@chromium.org

Review URL: https://codereview.chromium.org/585893002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24086 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Add fast path in MigrateFastToFast for following transitions that don't extend storage

BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/588553002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24087 ce2b1a6d-e550-0410-aec6-3dcde31c8c00