Allow asynchronous tests to explicitly register exceptions along with stack traces.

utils/tests/pub/test_pub.dart

Index: utils/tests/pub/test_pub.dart
diff --git a/utils/tests/pub/test_pub.dart b/utils/tests/pub/test_pub.dart
index 0cccbf959dcffb4fb4e509c931141ccf18672974..fabfb19c1c3f70690dbbc8d040581aa7111326ae 100644
--- a/utils/tests/pub/test_pub.dart
+++ b/utils/tests/pub/test_pub.dart
@@ -183,7 +183,8 @@ void run() {
     // that the test framework sees it, then finally call asyncDone so that the
     // test framework knows we're done doing asynchronous stuff.
     cleanup().then((_) {
-      guardAsync(() { throw error; }, asyncDone);
+      registerException(error, future.stackTrace);
+      asyncDone();
     });
     return true;
   });