Fix a browser crash when reading the disk cache experiment data after failing to map the index file.
Fix a browser crash when reading the disk cache experiment data
after failing to map the index file.

BUG=11414
TEST=none

Review URL: http://codereview.chromium.org/100349

git-svn-id: http://src.chromium.org/svn/trunk/src@15235 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: bbfd9b4aca91fb409c8688996a07a94a98543656
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