The current isolate tests don't work in drt/dartium because the
DOM isolate can't use Isolate.spawnFunction.
To avoid this problem, this change makes the affected tests start out
by doing an Isolate.spawnUri with their own main file, therevy running the test
in a non-DOM isolate. The test results are propagated back to the original
isolate.
I haven't been able to test dartium yet. I might be missing Selenium.
BUG= http://dartbug.com/14626R=floitsch@google.com
Review URL: https://codereview.chromium.org//70103014
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@30610 260f80e4-7a28-3924-810f-c04153c831b5