Don't use identical for null.
Don't use identical for null.

This was just a test to see if it generated the same code (it did),
but I forgot to revert it again.

R=fschneider@google.com

Review URL: https://codereview.chromium.org//578213002

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@40432 260f80e4-7a28-3924-810f-c04153c831b5

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