Slight rewording of compile-time errors for switch cases, for clarity. No semantic change.

R=rmacnak@google.com

Review URL: https://codereview.chromium.org//26650006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@28418 260f80e4-7a28-3924-810f-c04153c831b5
1 file changed