Release polymer 0.15.1

R=jakemac@google.com

Review URL: https://codereview.chromium.org//659563003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41108 260f80e4-7a28-3924-810f-c04153c831b5
Regenerate pub sources.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//657673002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41109 260f80e4-7a28-3924-810f-c04153c831b5
Fix pkgbuild tests for async_await.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//659613002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41110 260f80e4-7a28-3924-810f-c04153c831b5
pkg/shelf: only catch errors in createMiddleware if an errorHandler is provided

BUG= https://code.google.com/p/dart/issues/detail?id=21294
R=nweiz@google.com

Review URL: https://codereview.chromium.org//657543004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41111 260f80e4-7a28-3924-810f-c04153c831b5
Work around async_await#68 in pub.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//655943002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41112 260f80e4-7a28-3924-810f-c04153c831b5