Remove unmodifiable map wrappers that could instead use UnmodifiableMapView.

R=sgjesse@google.com

Review URL: https://codereview.chromium.org//214723002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/yaml@35244 260f80e4-7a28-3924-810f-c04153c831b5
1 file changed
tree: 6dce97a322c3ba24da8ba3c06c4b0ddb97f37591
  1. pkgs/