Sane asynchronous debugging and stack traces

runtime/observatory/tests/observatory_ui/mocks/repositories/target.dart

Index: runtime/observatory/tests/observatory_ui/mocks/repositories/target.dart
diff --git a/runtime/observatory/tests/observatory_ui/mocks/repositories/target.dart b/runtime/observatory/tests/observatory_ui/mocks/repositories/target.dart
index 1c7f3ede3f1ade7fd68e7cf0866a493100cdb0f6..4b563ee95d374840996792ccacaaa9660aa88be4 100644
--- a/runtime/observatory/tests/observatory_ui/mocks/repositories/target.dart
+++ b/runtime/observatory/tests/observatory_ui/mocks/repositories/target.dart
@@ -60,6 +60,10 @@ class TargetRepositoryMock implements M.TargetRepository {
     _onChange.add(new TargetChangeEventMock(repository: this));
   }
 
+  M.Target find(String networkAddress) {
+    return null;
+  }
+
   TargetRepositoryMock({M.Target current, Iterable<M.Target> list : const [],
       TargetRepositoryMockStringCallback add,
       TargetRepositoryMockTargetCallback setCurrent,