Unit test improvements.

The base config now sets things up so failed expects are routed through it.
A flag controls whether or not an expect failure stops the test (the default)
or if the test keeps pressing on.

Another flag has been added to disable the exception that gets thrown at the 
end of there were errors. The default remains to throw.

Finally, some cleaning up of test failure stacks is done. In particular we 
remove internal unittest frames from the stack.

R=sigmund@google.com

Review URL: https://codereview.chromium.org//14021021

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22186 260f80e4-7a28-3924-810f-c04153c831b5
3 files changed