Fixes issue #1907.  Puts parentheses around a comma expression that appears inside of an object literal.  Also adds tests to ensure correctness.

Patch by: sgross
Review by: me


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1604 8db76d5a-ed1c-0410-87a9-c151d255dfc7