fix ddc travis bot

pkg/dev_compiler/test/browser/language_tests.js

Index: pkg/dev_compiler/test/browser/language_tests.js
diff --git a/pkg/dev_compiler/test/browser/language_tests.js b/pkg/dev_compiler/test/browser/language_tests.js
index d61c34f4b647158b48121182bb54ddd141e9a79e..0003044f0b8e68f43bf1386435f4ca261bcdc0bb 100644
--- a/pkg/dev_compiler/test/browser/language_tests.js
+++ b/pkg/dev_compiler/test/browser/language_tests.js
@@ -230,7 +230,6 @@ define(['dart_sdk', 'async_helper', 'expect', 'unittest', 'is', 'require',
       'big_integer_parsed_arith_vm_test': fail,
       'big_integer_parsed_div_rem_vm_test': fail,
       'big_integer_parsed_mul_div_vm_test': fail,
-
       'bit_twiddling_bigint_test': fail,
       'collection_length_test': skip_timeout,
       'compare_to2_test': fail,
@@ -240,6 +239,8 @@ define(['dart_sdk', 'async_helper', 'expect', 'unittest', 'is', 'require',
       'core_runtime_types_test': fail,
       'date_time10_test': fail,
       'double_parse_test_02_multi': firefox_fail,
+      'error_stack_trace_test_nullThrown_multi': fail,
+      'list_unmodifiable_test': fail, // DDC is throwing a strong mode error, so it may be a test bug
       'for_in_test': is.firefox('<=50') ? fail : pass,
       'growable_list_test': fail,
       'hash_map2_test': skip_timeout,