Optimize DDC private library files.

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 9720ecf6efaec9fd4baa46d1ad8876c0d5203176..f5e16a5c4f7cc2574c89ee87ee0b299a9918deac 100644
--- a/pkg/dev_compiler/test/browser/language_tests.js
+++ b/pkg/dev_compiler/test/browser/language_tests.js
@@ -241,7 +241,6 @@ define(['dart_sdk', 'async_helper', 'expect', 'unittest', 'is', 'require',
       '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,
@@ -255,6 +254,7 @@ define(['dart_sdk', 'async_helper', 'expect', 'unittest', 'is', 'require',
       'int_parse_with_limited_ints_test': fail,
       'integer_to_radix_string_test': fail,
       'integer_to_string_test_01_multi': fail,
+      'iterable_fold_test_02_multi': fail,
       'iterable_return_type_test_02_multi': fail,
       'json_map_test': fail,
       'list_fill_range_test': fail,