Pass in "mode" to transformer plugins.
Pass in "mode" to transformer plugins.

BUG=https://code.google.com/p/dart/issues/detail?id=14538
R=nweiz@google.com, sigmund@google.com

Review URL: https://codereview.chromium.org//52853004

git-svn-id: 0aa7e0b98478d6ef7145d04e8154f8ab2209deba@29690 260f80e4-7a28-3924-810f-c04153c831b5

meflyup/polymer-dart,ronlobo/polymer-dart,dam0vm3nt/polymer-dart,dart-archive/polymer-dart,jakemac53/polymer-dart,dart-archive/polymer-dart,meflyup/polymer-dart,ronlobo/polymer-dart,dam0vm3nt/polymer-dart,jakemac53/polymer-dart