[dartdevc] small cleanup tweaks to the ddb tool
[dartdevc] small cleanup tweaks to the ddb tool

Change-Id: I4691fbe24d94f7efca03c1c3c40a0a8cac20082c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/176983
Reviewed-by: Mark Zhou <654f5fe0c4ca6c799b0e735dcf3fc1c389f35bf9@google.com>
Commit-Queue: Sigmund Cherem <beaea8fd7d2a56555046ba4f362c8a93e3938576@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk