Drop return types in DeclarationMatcher visitor.

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//738343002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41853 260f80e4-7a28-3924-810f-c04153c831b5
Infrastructure for testing IncrementalResolver.

It should help in tesing incremental resolution of any changed node.

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//744553002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41854 260f80e4-7a28-3924-810f-c04153c831b5