dart2js: accept const map literals as expression statements.

tests/co19/co19-dart2js.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.
 
 [ $compiler == dart2js && $runtime == jsshell ]
 LibTest/core/List/sort_A01_t04: Fail, Pass, Timeout # Must be a bug in jsshell, test sometimes times out.
 
 # Crashes first, please. Then untriaged bugs. There is a section below
 # for co19 bugs.
 [ $compiler == dart2js ]
@@ skipping 420 matching lines @@
 Language/12_Expressions/12_Instance_Creation/1_New_A02_t03: fail # Issue 21092 and co19 issue 713
 Language/12_Expressions/12_Instance_Creation/1_New_A02_t05: fail # Issue 21092 and co19 issue 713
 Language/12_Expressions/12_Instance_Creation/1_New_A02_t06: fail # Issue 21092 and co19 issue 713
 Language/12_Expressions/12_Instance_Creation/1_New_A02_t07: fail # Issue 21092 and co19 issue 713
 Language/12_Expressions/12_Instance_Creation/2_Const_A11_t01: fail # Issue 21134 and co19 issue 714
 Language/12_Expressions/12_Instance_Creation/2_Const_A11_t03: fail # Issue 21134 and co19 issue 714
 Language/12_Expressions/22_Equality_A01_t01: fail # Issue 21137
 Language/12_Expressions/22_Equality_A05_t01: fail # Issue 21137
 Language/12_Expressions/30_Identifier_Reference_A02_t01: fail # Issue 21154
 Language/12_Expressions/33_Type_Cast_A02_t03: fail # co19 issue 716
-Language/13_Statements/02_Expression_Statements_A01_t08: fail # Issue 21155
 Language/13_Statements/10_Rethrow_A01_t04: fail # co19 issue 719
 Language/13_Statements/10_Rethrow_A01_t05: fail # co19 issue 719
 Language/14_Libraries_and_Scripts/1_Imports_A03_t08: fail # Issue 21171
 Language/14_Libraries_and_Scripts/1_Imports_A03_t09: fail # Issue 21171
 Language/14_Libraries_and_Scripts/1_Imports_A03_t10: fail # Issue 21171
 Language/14_Libraries_and_Scripts/1_Imports_A03_t28: fail # Issue 21171
 Language/14_Libraries_and_Scripts/1_Imports_A03_t29: fail # co19 issue 723
 Language/14_Libraries_and_Scripts/1_Imports_A03_t30: fail # co19 issue 723
 Language/15_Types/4_Interface_Types_A11_t01: crash # Issue 21174
 Language/15_Types/4_Interface_Types_A11_t02: crash # Issue 21174
@@ skipping 180 matching lines @@
 LibTest/convert/JsonCodec/encode_A01_t01: RuntimeError # co19-roll r641: Please triage this failure
 LibTest/convert/JsonCodec/encode_A01_t02: RuntimeError # co19-roll r641: Please triage this failure
 
 [ $compiler == dart2js && $runtime == d8 && $system == windows ]
 LibTest/async/DeferredLibrary/*: Skip # Issue 17458
 
 [ $compiler == dart2js && $mode == debug ]
 LibTest/collection/ListBase/ListBase_class_A01_t01: Pass, Timeout
 LibTest/collection/ListMixin/ListMixin_class_A01_t01: Pass, Timeout
 LibTest/core/List/List_class_A01_t01: Pass, Timeout