Another fix for unused elements.
Another fix for unused elements.

It turned out that the way I run analyzer tests misses the new task model tests.
And (un)fortunately bots run them correctly, so some of the are red now.

TBR

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//1089653002

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@45180 260f80e4-7a28-3924-810f-c04153c831b5

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