Previously we could return "invalid path" responses for any non-Dart files. This allows clients to send requests for other files and just successful (though empty) responses.
Change-Id: I192e83ac2ebd2124c03c22e3e048a066cfd33f17
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/101990
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Danny Tuppeny <dantup@google.com>