Fixes regressions in @UiHandler.

Change-Id: Id929d771ed05d8a25f49d2c9256dc44ee034f7c3
Review-Link: https://gwt-review.googlesource.com/#/c/6175/
(cherry picked from commit 12a8262eb2534f79af49e2a830eb7a5b770cba87)
3 files changed