Fix test status

pkg/dev_compiler/test/not_yet_strong_tests.dart

 import 'dart:collection';
 
 /// The set of tests that are not yet strong mode safe.
 final notYetStrongTests = new HashSet<String>.from([
   'language/abstract_exact_selector_test_01_multi',
   'language/abstract_factory_constructor_test_00_multi',
   'language/abstract_getter_test_01_multi',
   'language/abstract_runtime_error_test_01_multi',
   'language/abstract_runtime_error_test_02_multi',
   'language/abstract_runtime_error_test_03_multi',
@@ skipping 766 matching lines @@
   'language/function_type_call_getter2_test_04_multi',
   'language/function_type_call_getter2_test_05_multi',
   'language/function_type_test',
   'language/generic_closure_test',
   'language/generic_constructor_mixin2_test',
   'language/generic_constructor_mixin3_test',
   'language/generic_constructor_mixin_test',
   'language/generic_field_mixin6_test_01_multi',
   'language/generic_field_mixin6_test_none_multi',
   'language/generic_list_checked_test',
+  'language/generic_tearoff_test',
   'language/generic_test',
   'language/generics_test',
   'language/get_set_syntax_test_00_multi',
   'language/get_set_syntax_test_01_multi',
   'language/get_set_syntax_test_02_multi',
   'language/get_set_syntax_test_03_multi',
   'language/get_set_syntax_test_04_multi',
   'language/get_set_syntax_test_05_multi',
   'language/get_set_syntax_test_06_multi',
   'language/get_set_syntax_test_07_multi',
@@ skipping 397 matching lines @@
   'language/mixin_invalid_bound_test_none_multi',
   'language/mixin_invalid_inheritance1_test_01_multi',
   'language/mixin_invalid_inheritance1_test_02_multi',
   'language/mixin_invalid_inheritance1_test_03_multi',
   'language/mixin_invalid_inheritance2_test_01_multi',
   'language/mixin_invalid_inheritance2_test_02_multi',
   'language/mixin_invalid_inheritance2_test_03_multi',
   'language/mixin_lib_extends_field_test',
   'language/mixin_lib_extends_method_test',
   'language/mixin_method_test',
-  'language/mixin_mixin_bound_test', // issue 28450
   'language/mixin_super_bound2_test_01_multi',
   'language/mixin_super_bound2_test_none_multi',
   'language/mixin_super_bound_test',
   'language/mixin_super_constructor2_test',
   'language/mixin_super_constructor_default_test',
   'language/mixin_super_constructor_named_test_01_multi',
   'language/mixin_super_constructor_named_test_none_multi',
   'language/mixin_super_constructor_positionals_test_01_multi',
   'language/mixin_super_constructor_positionals_test_none_multi',
   'language/mixin_super_constructor_test',
@@ skipping 903 matching lines @@
   'lib/mirrors/fake_function_without_call_test',
   'lib/mirrors/generic_bounded_by_type_parameter_test_01_multi',
   'lib/mirrors/generic_bounded_by_type_parameter_test_02_multi',
   'lib/mirrors/generic_bounded_by_type_parameter_test_none_multi',
   'lib/mirrors/generic_bounded_test_01_multi',
   'lib/mirrors/generic_bounded_test_02_multi',
   'lib/mirrors/generic_bounded_test_none_multi',
   'lib/mirrors/generic_class_declaration_test',
   'lib/mirrors/generic_f_bounded_mixin_application_test',
   'lib/mirrors/generic_interface_test_01_multi',
-  'lib/mirrors/generics_dynamic_test', // issue 28450
   'lib/mirrors/generics_test_01_multi',
   'lib/mirrors/get_symbol_name_no_such_method_test',
   'lib/mirrors/immutable_collections_test',
   'lib/mirrors/inference_and_no_such_method_test',
   'lib/mirrors/inherit_field_test',
   'lib/mirrors/initializing_formals_test_01_multi',
   'lib/mirrors/initializing_formals_test_03_multi',
   'lib/mirrors/initializing_formals_test_none_multi',
   'lib/mirrors/instance_members_easier_test',
   'lib/mirrors/instance_members_test',
@@ skipping 280 matching lines @@
   'lib/html/mutationobserver_test',
   'lib/html/postmessage_structured_test',
   'lib/html/resource_http_test',
   'lib/html/transferables_test',
   'lib/html/webgl_1_test',
   'lib/html/wrapping_collections_test',
   // TODO(jmesserly): these are both under "dart:html" as well.
   'js_test',
   'js_util_test'
 ]);