Adapt analyzer to new warnings around switch-case fallthrough.
Adapt analyzer to new warnings around switch-case fallthrough.

Fixes issue #27664.
BUG= http://dartbug.com/27664
R=brianwilkerson@google.com

Review URL: https://codereview.chromium.org/2446093003 .

Committed: https://github.com/dart-lang/sdk/commit/1322877f5b3a8c741d73df861169c494311073e8

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