Include command in ProcessException.

R=sgjesse@google.com
BUG=dartbug.com/4060

Review URL: https://codereview.chromium.org//11417028

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@15010 260f80e4-7a28-3924-810f-c04153c831b5
2 files changed