Don't match directly on gzip output of empty message, as it's not strictly specified.
Don't match directly on gzip output of empty message, as it's not strictly specified.

Fixes test failure on Windows.

BUG=
R=lrn@google.com

Review URL: https://codereview.chromium.org//183763021

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@33211 260f80e4-7a28-3924-810f-c04153c831b5

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