Use filtered stacks in pub, barback, and watcher tests.
Use filtered stacks in pub, barback, and watcher tests.

This also exposes more unittest stuff to users of scheduled_test.

R=rnystrom@google.com
BUG=

Review URL: https://codereview.chromium.org//23582003

git-svn-id: a962b240025cf0577aa172e20f49ccb159ba6be1@26751 260f80e4-7a28-3924-810f-c04153c831b5

maxwellpeterson-wf/pub,computmaxer/pub,dart-lang/pub,cjkao/dart-pub,dart-lang/pub