Implement 'as' operator.

tests/language/language.status

 # Copyright (c) 2012, 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.
 
 # This directory contains tests that are intended to show the
 # current state of the language.
 
 # In order to maintain maximum test coverage for all builds,
 # please use the following procedure to mark a test
 # failed on architectures other than the one you are working on.
 #
 # 1) Copy the old version of the test to
 #    tests/language/src/test_name_[dartc|vm]_test.dart.
 #    to maintain coverage.
 # 2) File a bug on each architecture for the failure due to the language change.
 # 3) Update the language/src directory with the updated test.
 
 [ $compiler == none ]
+cast_test: Fail # Issue 3400
 gc_test: Fail # Issue 1487
 field_override_test/none: Fail  # Issue 742: field shadowing now allowed
 field_override_test/01: Fail    # Issue 742: field shadowing now allowed
 field_override_test/02: Fail    # Issue 742: field shadowing now allowed
 super_field_access_test: Fail    # Issue 742: field shadowing now allowed
 pseudo_kw_illegal_test/03: Fail  # Issue 356
 pseudo_kw_illegal_test/08: Fail  # Issue 356
 pseudo_kw_illegal_test/10: Fail  # Issue 356
 pseudo_kw_illegal_test/14: Fail  # Issue 356
 
@@ skipping 17 matching lines @@
 
 constructor_redirect_test/01: Fail # Issue 2103.
 
 closure_with_super_send_test: Fail # Issue 3197.
 super_closure_test: Fail # Issue 3197.
 parameter_initializer6_negative_test: Fail # Issue 3502
 
 prefix_core_test: Fail # Issue 3638.
 
 # Issue 2501
-cascade_test: Pass,Fail  # Some cases pass, but for the wrong reason  
-cascade_precedence_test: Fail 
+cascade_test: Pass,Fail  # Some cases pass, but for the wrong reason
+cascade_precedence_test: Fail
 
 fauxverride_test/none: Fail # Issue 3778.
 
 # DartC specific tests that should not be run by the VM
 *dartc_test: Skip
 *dartc_negative_test: Skip
 
 [ $compiler == none && $mode == debug ]
 gc_test: Skip  # Takes too long.
 
 [ $compiler == dartc ]
 application_negative_test: Fail # Runtime only test, rewrite as multitest
 assert_keyword_negative_test: Fail # Runtime only test, rewrite as multitest
 assign_instance_method_negative_test: Fail  # Issue 3662
 body_less_constructor_wrong_arg_negative_test: Fail  # Runtime only test, rewrite as multitest
-call_operator_test: Pass # Issue 1355  
+call_operator_test: Pass # Issue 1355
 cascade_test: Pass,Fail # Issue 3729  Some cases pass, but for the wrong reason
 cascade_precedence_test: Fail  # Issue 3729
+cast_test: Fail  # Issue 3401
 char_escape_test: Pass # Issue 1654
 closure_call_wrong_argument_count_negative_test: Fail # Runtime only test, rewrite as multitest
 compile_time_constant_p_test/01: Fail # Issue 2580
 const_syntax_test/01: Fail # test issue 3626
 const_syntax_test/02: Fail # test issue 3626
 const_syntax_test/03: Fail # test issue 3626
 constructor3_negative_test: Fail # Runtime only test, rewrite as multitest
 constructor_call_wrong_argument_count_negative_test: Fail # Runtime only test, rewrite as multitest
 default_factory_library_test: Fail          # Issue 514
 disable_privacy_test: Skip  # Issue 1882: Needs --disable_privacy support.
 duplicate_implements_test: Skip # Issue 976
 factory5_test/00: Fail # issue 3079
-field3a_negative_test: Fail # Issue 3655  
+field3a_negative_test: Fail # Issue 3655
 field_method4_negative_test: Fail  # Runtime only test, rewrite as multitest
 final_syntax_test/*: Skip  # can't handle base case
 instance_call_wrong_argument_count_negative_test: Fail # Runtime only test, rewrite as multitest
 library2_negative_test: Fail # still a valid test? Issue 3649
 library4_negative_test: Fail # still a valid test? Issue 3530
 library6_negative_test: Fail # still a valid test? Issue 3650
 list_literal4_test: Fail       # Issue 1343
 map_literal4_test: Fail        # Issue 1343
 named_parameters_negative_test: Fail # Runtime only test, rewrite as multitest
 named_parameters_with_object_property_names_test: Fail # Issue 2137
-no_such_method_negative_test: Fail # Runtime only test, rewrite as multitest 
+no_such_method_negative_test: Fail # Runtime only test, rewrite as multitest
 override_field_test/04: Fail # Issue 3656
 private_member3_negative_test: Fail # Runtime only test?  rewrite as multitest
 pseudo_kw_illegal_test/08: Fail # Issue 356
 pseudo_kw_illegal_test/10: Fail # Issue 356
 pseudo_kw_illegal_test/14: Fail # Issue 356
 static_call_wrong_argument_count_negative_test: Fail # Runtime only test, rewrite as multitest
 switch7_negative_test: Fail    # Issue 3658
 switch_label_test: Fail        # Issue 3658
 syntax_test: Skip              # Bug 2107  Static type warnings in none case
 third_test: Fail               # Issue 3659
@@ skipping 33 matching lines @@
 *: Skip
 
 [ $browser ]
 prefix_core_test: Fail # Issue 2264.
 
 [ $arch == simarm ]
 *: Skip
 
 [ $arch == arm ]
 *: Skip