Let docgen detect a dart-sdk directory that's differently named, and do it correctly on bleeding edge

BUG=
R=ricow@google.com

Review URL: https://codereview.chromium.org//737033002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42112 260f80e4-7a28-3924-810f-c04153c831b5
Add an option for incremental resolution of API breaking changes.

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//781783002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42113 260f80e4-7a28-3924-810f-c04153c831b5
update to polymer js 0.5.1

BUG= http://dartbug.com/21583
R=sigmund@google.com

Review URL: https://codereview.chromium.org//723393003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42114 260f80e4-7a28-3924-810f-c04153c831b5