Purge memory for DBs in the renderer process.
Purge memory for DBs in the renderer process.

BUG=23400
TEST=none
Review URL: http://codereview.chromium.org/350012

git-svn-id: http://src.chromium.org/svn/trunk/src@30723 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 980c63a1a296f1c9b0c3600a54a7809bc2f2e962
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