Removes duplicate method dispatchers generated by GWTTestCase.

This also adds test cases to verify GWTTestCase correctly handles inheritance.

Change-Id: I52fe1d3ee60ec4c289e4055653125253c5639e76
Review-Link: https://gwt-review.googlesource.com/#/c/2590/

Review by: mdempsky@google.com
Sets the throwable's message when converting Json to LogRecord.

Review-Link: https://gwt-review.googlesource.com/#/c/2310/
Upgrade JDT to 3.8.3.

Change-Id: If7d533adcb953de614ea071cfd7e57560b664ce0
Review-Link: https://gwt-review.googlesource.com/#/c/2361/
Verify that Timer has not been canceled before firing

* cancelTimeout is not always effective with older versions of IE
* Add cancelCounter that is updated when canceling and verified when firing
* Fixes Issue 8101

Change-Id: I0ac16598bef878ed756f2fe0dc696166f2a3d504
Review-Link: https://gwt-review.googlesource.com/#/c/2511/

Review by: mdempsky@google.com