Hack fix to include Mock in the API documentation.

pkg/unittest/lib/unittest.dart

Index: pkg/unittest/lib/unittest.dart
diff --git a/pkg/unittest/lib/unittest.dart b/pkg/unittest/lib/unittest.dart
index 87a6f9dc57390e7ce5bb86982183bb0687fd3b6b..5bf1feb585c06514d1835b783253d085de3787f1 100644
--- a/pkg/unittest/lib/unittest.dart
+++ b/pkg/unittest/lib/unittest.dart
@@ -151,6 +151,10 @@ import 'dart:isolate';
 import 'matcher.dart';
 export 'matcher.dart';
 
+// TODO(amouravski): We should not need to import mock here, but it's necessary
+// to enable dartdoc on the mock library, as it's not picked up normally.
+import 'mock.dart';
+
 part 'src/config.dart';
 part 'src/test_case.dart';