Mention that OAuth2 currently only works with dart:io.

R=rnystrom@google.com
BUG=7445

Review URL: https://codereview.chromium.org//61393004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@30296 260f80e4-7a28-3924-810f-c04153c831b5
1 file changed
tree: c2106f4961f0eeb8595ce0875a62f4b5ca67ff11
  1. lib/
  2. test/
  3. pubspec.yaml