Mark try/end_to_end_test as slow.
Mark try/end_to_end_test as slow.

The test times out on the chrome-linux bots but seems to run OK on chrome-windows, so let's try to give a bit more time.

R=floitsch@google.com

Review URL: https://codereview.chromium.org//357623002

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@37683 260f80e4-7a28-3924-810f-c04153c831b5

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