Fix ddbg completers
Fix ddbg completers

The debugger tool now depends on command completers being executed
synchronously, so create completes with the proper constructor.

This fixes occasional assertions that an isolate is paused when stepping.

R=iposva@google.com

Review URL: https://codereview.chromium.org//85003003

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@30639 260f80e4-7a28-3924-810f-c04153c831b5

dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk