Add support for running slices of the layout tests continuously rather than as one big lump.
Add support for running slices of the layout tests continuously rather than as one big lump.

Review URL: http://codereview.chromium.org/13696

git-svn-id: http://src.chromium.org/svn/trunk/src@6742 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 4b2c02988823584a75a4cbd85d309bfdd4e58861
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser