dart2js: Support eagerly initialized classes in new emitter.

Supersedes https://codereview.chromium.org/647023005/

R=kasperl@google.com

Review URL: https://codereview.chromium.org//650953003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41243 260f80e4-7a28-3924-810f-c04153c831b5