Chrome proxy service test case is failing in latest dev release

[elliette]

test case succeeds on 3.0.0-0.0.dev, fails on 3.0.0-21.0.dev:

00:15 +0 -1: shared context getStack break on exceptions with legacy setExceptionPauseMode [E]
  Expected: contains 'main.dart'
    Actual: <null>
     Which: is not a string, map or iterable