Improve nomenclature of new AnalysisContext async method.

R=danrubel@google.com

Review URL: https://codereview.chromium.org//809793002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42404 260f80e4-7a28-3924-810f-c04153c831b5
Cleanup access to Instruction's fields (especially deopt_id_).

R=johnmccutchan@google.com

Review URL: https://codereview.chromium.org//806973002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42405 260f80e4-7a28-3924-810f-c04153c831b5