Enable string impl caching for test shell to improve test coverage.
Enable string impl caching for test shell to improve test coverage.

Patch by Anton Muhin
R=darin
BUG=none
TEST=none



git-svn-id: http://src.chromium.org/svn/trunk/src@22156 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 09ff0332dc38a4ce15d853842b6fb2fdfe3401cf
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