Add StringLengthConstantExpression

tests/compiler/dart2js/semantic_visitor_test_send_data.dart

Index: tests/compiler/dart2js/semantic_visitor_test_send_data.dart
diff --git a/tests/compiler/dart2js/semantic_visitor_test_send_data.dart b/tests/compiler/dart2js/semantic_visitor_test_send_data.dart
index 23460295bf30a62fa6f97d97aa62827d888d5ad2..077b9c01e31f276e402c0fd757a69567e14955eb 100644
--- a/tests/compiler/dart2js/semantic_visitor_test_send_data.dart
+++ b/tests/compiler/dart2js/semantic_visitor_test_send_data.dart
@@ -3093,7 +3093,7 @@ const Map<String, List<Test>> SEND_TESTS = const {
         ''',
         const Visit(VisitKind.VISIT_BOOL_FROM_ENVIRONMENT_CONSTRUCTOR_INVOKE,
             constant:
-                'const bool.fromEnvironment("foo", defaultValue: false)')),
+                'const bool.fromEnvironment("foo")')),
     const Test(
         '''
         m() => const bool.fromEnvironment('foo', defaultValue: true);
@@ -3105,14 +3105,14 @@ const Map<String, List<Test>> SEND_TESTS = const {
         m() => const int.fromEnvironment('foo');
         ''',
         const Visit(VisitKind.VISIT_INT_FROM_ENVIRONMENT_CONSTRUCTOR_INVOKE,
-            constant: 'const int.fromEnvironment("foo", defaultValue: null)')),
+            constant: 'const int.fromEnvironment("foo")')),
     const Test(
         '''
         m() => const String.fromEnvironment('foo');
         ''',
         const Visit(VisitKind.VISIT_STRING_FROM_ENVIRONMENT_CONSTRUCTOR_INVOKE,
             constant:
-                'const String.fromEnvironment("foo", defaultValue: null)')),
+                'const String.fromEnvironment("foo")')),
     const Test(
         '''
         class Class {