Add message to rebaseline.sh
Add message to rebaseline.sh

The rebaseline tool now works on the upstream test_expectations.txt.
If someone adds a REBASELINE tag to the local version we'll now print
a (hopefully) helpful message telling them what's up.

git-svn-id: http://src.chromium.org/svn/trunk/src@45577 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 8e0229c1c2dcdace556b6e41f8b9e34a407ca609
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