Cleanup waterfall.sh.
Cleanup waterfall.sh.

Use /bin/bash instead of /bin/sh
Use either curl or wget, depending on what is installed
Bail out of a download fails

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/3142003

git-svn-id: http://src.chromium.org/svn/trunk/src@55543 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 94d3968dbea15a1a1eeffc55e2cb75af59ec61f3
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