Allow null assignments if there is a corresponding marker.

R=podivlov@chromium.org
BUG=10025

Review URL: https://codereview.chromium.org//14190019

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22067 260f80e4-7a28-3924-810f-c04153c831b5
2 files changed