Adds more widget creation benchmarks. to compare creating via innerHTML v. dom
calls, and empty dom structures v. similar structures with a bit of text.

Reviewed by jgw
http://gwt-code-reviews.appspot.com/129804

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7366 8db76d5a-ed1c-0410-87a9-c151d255dfc7