increased zIndex of compile dialog to avoid it being hidden

Change-Id: Id1a541fc108e0a9087276a3fe104f5ec129e56cf
Review-Link: https://gwt-review.googlesource.com/#/c/1530/

Review by: skybrian@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11456 8db76d5a-ed1c-0410-87a9-c151d255dfc7