Migrate async tests to strong

pkg/dev_compiler/test/not_yet_strong_tests.dart

Index: pkg/dev_compiler/test/not_yet_strong_tests.dart
diff --git a/pkg/dev_compiler/test/not_yet_strong_tests.dart b/pkg/dev_compiler/test/not_yet_strong_tests.dart
index ca2b1cb5e98f4c12ee74341451200c335b29ee49..d5c5092a83d8922021d01b0f9a43482af0ac3ad0 100644
--- a/pkg/dev_compiler/test/not_yet_strong_tests.dart
+++ b/pkg/dev_compiler/test/not_yet_strong_tests.dart
@@ -2090,6 +2090,25 @@ final notYetStrongTests = new HashSet<String>.from([
   'corelib/symbol_test_none_multi',
   'corelib/uri_path_test',
   'corelib/uri_query_test',
+  'lib/async/async_await_sync_completer_test',
+  'lib/async/async_await_zones_test',
+  'lib/async/catch_errors2_test',
+  'lib/async/catch_errors3_test',
+  'lib/async/catch_errors_test',
+  'lib/async/future_microtask_test',
+  'lib/async/future_or_bad_type_test_00_multi',
+  'lib/async/future_or_bad_type_test_01_multi',
+  'lib/async/future_or_only_in_async_test_00_multi',
+  'lib/async/future_test_none_multi',
+  'lib/async/future_test_01_multi',
+  'lib/async/future_value_chain4_test',
+  'lib/async/print_test_01_multi',
+  'lib/async/print_test_none_multi',
+  'lib/async/slow_consumer3_test',
+  'lib/async/stream_controller_test',
+  'lib/async/stream_event_transformed_test',
+  'lib/async/stream_transformer_test',
+  'lib/async/zone_debug_test',
   'lib/convert/chunked_conversion1_test',
   'lib/math/min_max_test',
   'lib/typed_data/float32x4_test',