Cleans up few remaning issues from recent clean up in test infra.

- Removes JUnitTestCaseStubGenerator as it is no longer used with removal of benchmark and gwt runner generator.
- Removes user agent accessor as it is no longer accessed externally.

Change-Id: I271672e7da471f1c27e6bb42266d49dcf507566d
Review-Link: https://gwt-review.googlesource.com/#/c/2050/

Review by: mdempsky@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11536 8db76d5a-ed1c-0410-87a9-c151d255dfc7
3 files changed