Disabling some tests in ImageTest because Chrome fires onload synchronously. I will address this issue later.

Patch by: jlabanca
Review by: jgw (desk)
Issue: 863



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@6588 8db76d5a-ed1c-0410-87a9-c151d255dfc7