dart:platform | Fix isolate_test on Dartium.
dart:platform | Fix isolate_test on Dartium.

Change lib/platform/isolate_test to use package:expect instead of package:unittest, so spawnFunction will work on Dartium.

BUG=
R=sgjesse@google.com

Review URL: https://codereview.chromium.org//44303002

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@29251 260f80e4-7a28-3924-810f-c04153c831b5

dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk