Adding support for `sourceRoot` to the SingleMapping class.

BUG=
R=sigmund@google.com

Review URL: https://codereview.chromium.org//383823002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/source_maps@38241 260f80e4-7a28-3924-810f-c04153c831b5
2 files changed
tree: 79284ddcf651247aa9a9188b4ce926fd4ff14274
  1. pkgs/