Add Compiler.forgetElement.

R=johnniwinther@google.com

Review URL: https://codereview.chromium.org//593643002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@40748 260f80e4-7a28-3924-810f-c04153c831b5
Include 'potentialEdits' into refactoring feedback.

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//611823003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@40750 260f80e4-7a28-3924-810f-c04153c831b5
Display the 'final' overlay for elements.

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//614593002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@40751 260f80e4-7a28-3924-810f-c04153c831b5