Move elementAccess from namer to emitter.

R=floitsch@google.com

Review URL: https://codereview.chromium.org//779593002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42130 260f80e4-7a28-3924-810f-c04153c831b5
Reenable check_elements_invariants_test

BUG=http://dartbug.com/21452
R=karlklose@google.com

Review URL: https://codereview.chromium.org//686023002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42131 260f80e4-7a28-3924-810f-c04153c831b5