fix list_test for strong mode, and fix DDC List constructors

tests/corelib_2/corelib_2.status

 # Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # All static_tests have expected compile-time errors.
 [ $strong && $compiler != dart2analyzer && $compiler != dartdevc ]
 core_runtime_types_static_test: MissingCompileTimeError
 splay_tree_test/01: MissingCompileTimeError
 splay_tree_test/02: MissingCompileTimeError
 string_base_vm_static_test: MissingCompileTimeError
@@ skipping 78 matching lines @@
 big_integer_parsed_arith_vm_test: RuntimeError # Issue 29921
 const_list_literal_test: RuntimeError # Issue 29921
 const_list_remove_range_test: RuntimeError # Issue 29921
 const_list_set_range_test: RuntimeError # Issue 29921
 compare_to2_test: RuntimeError # Issue 30170
 date_time10_test: RuntimeError # Issue 29921
 growable_list_test: RuntimeError # Issue 29921
 hash_set_test/01: RuntimeError # Issue 29921
 iterable_reduce_test/none: RuntimeError
 iterable_to_list_test/*: RuntimeError
-list_test/none: RuntimeError
-list_test/01: RuntimeError
+list_concurrent_modification_test: RuntimeError # DDC uses ES6 array iterators so it does not issue this
 nan_infinity_test/01: RuntimeError # Issue 29921
 null_nosuchmethod_test: RuntimeError # Issue 29921
 main_test: RuntimeError # Issue 29921
 map_test: RuntimeError # Issue 29921
 map_keys2_test: RuntimeError # Issue 29921
 regexp/bol-with-multiline_test: RuntimeError # Issue 29921
 regexp/invalid-range-in-class_test: RuntimeError # Issue 29921
 regexp/look-ahead_test: RuntimeError # Issue 29921
 regexp/loop-capture_test: RuntimeError # Issue 29921
 regexp/malformed-escapes_test: RuntimeError # Issue 29921
@@ skipping 63 matching lines @@
 regress_r21715_test: RuntimeError # Requires bigint support.
 int_parse_with_limited_ints_test: Skip # dart2js and dartdevc don't know about --limit-ints-to-64-bits
 typed_data_with_limited_ints_test: Skip # dart2js and dartdevc don't know about --limit-ints-to-64-bits
 
 [ $compiler == dart2js && $runtime != none ]
 nan_infinity_test/01: RuntimeError
 integer_to_string_test/01: RuntimeError
 iterable_to_set_test: RuntimeError # is-checks do not implement strong mode type system
 int_parse_radix_test/01: RuntimeError
 int_parse_radix_test/02: RuntimeError
+list_test/*: RuntimeError # dart2js doesn't implement strong mode covariance checks
 
 [ $compiler == dart2js && $runtime == drt && $csp && $minified ]
 core_runtime_types_test: Pass, Fail # Issue 27913
 
 [ $compiler != dartdevc ]
 error_stack_trace_test/static: MissingCompileTimeError
 iterable_element_at_test/static: MissingCompileTimeError
 
 [ $compiler == dartdevc && $runtime != none ]
 error_stack_trace_test/nullThrown: RuntimeError # .stackTrace not present for exception caught from 'throw null;'
@@ skipping 125 matching lines @@
 big_integer_parsed_mul_div_vm_test: Pass, SloW
 int_parse_radix_test/*: Pass, Slow
 
 [ $compiler == precompiler ]
 big_integer_parsed_mul_div_vm_test: Pass, Timeout # --no_intrinsify
 
 [ $compiler == none && ($runtime == vm || $runtime == flutter)]
 string_trimlr_test/02: RuntimeError # Issue 29060
 iterable_to_set_test: RuntimeError # is-checks do not implement strong mode type system
 
+
 [ $compiler == precompiler || $compiler == app_jit ]
 string_trimlr_test/02: RuntimeError # Issue 29060
 
 # void should be a valid symbol.
 [ $compiler == none || $compiler == precompiler || $compiler == app_jit || ($compiler == dart2js && !$dart2js_with_kernel) ]
 symbol_reserved_word_test/02: CompileTimeError # Issue 20191
 
 # With the exception of 'void', const Symbol() should not accept reserved
 # words.
 symbol_reserved_word_test/04: MissingCompileTimeError # Issue 11669, 19972
@@ skipping 590 matching lines @@
 splay_tree_from_iterable_test: RuntimeError
 
 [ $compiler == precompiler && $runtime == dart_precompiled && !$checked ]
 iterable_generate_test/01: RuntimeError
 splay_tree_from_iterable_test: RuntimeError
 
 [ $runtime == vm || $runtime == dart_precompiled || $runtime == flutter ]
 regexp/pcre_test: Pass, Slow, Timeout
 regexp/global_test: Skip # Issue 21709
 
+[ $runtime == vm || $runtime == dart_precompiled ]
+list_test/*: RuntimeError # VM doesn't implement strong mode covariance checks
+
 [ $mode == debug ]
 regexp/pcre_test: Pass, Slow # Issue 22008
 
 [ $compiler == dart2js && ! $browser ]
 package_resource_test: RuntimeError # Issue 26842
 
 [ $compiler == dart2js && ! $dart2js_with_kernel ]
 list_unmodifiable_test: Pass, RuntimeError # Issue 28712
 iterable_to_list_test/01: RuntimeError # Issue 26501
 iterable_return_type_test/01: RuntimeError # Issue 20085
 iterable_return_type_test/02: RuntimeError # Dart2js does not support Uint64*.
 
 [ $compiler == dart2analyzer ]
 int_parse_radix_bad_handler_test: MissingCompileTimeError
 iterable_element_at_test/static: Pass
 
 [ $compiler == dart2analyzer && $strong ]
 int_parse_radix_bad_handler_test: Pass
 
 [ $compiler == dart2analyzer && $strong && $checked ]
 iterable_fold_test/01: CompileTimeError
 
 [ $compiler == dart2analyzer && $checked && !$strong ]
 iterable_fold_test/01: Pass
 
 [ $compiler == dart2analyzer && $strong  && !$checked ]
 iterable_fold_test/01: CompileTimeError