Guard against directory traversal due to evil message from compromised renderer.
Guard against directory traversal due to evil message from compromised
renderer.

TEST=NONE
BUG=29828

Review URL: http://codereview.chromium.org/467061

git-svn-id: http://src.chromium.org/svn/trunk/src@34264 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 3d0494c15a0d09e717873fb3d5eefa439773a57a
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