Handle deferred access as pre-step in SemanticSendVisitor.

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
index 3ecb2745ff0ca6199dc76d99e6324a4351623e6e..dedaac8b419e0f1e85062d142d4509b81b1be733 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
@@ -612,6 +612,11 @@ abstract class IrBuilderVisitor extends ast.Visitor<ir.Primitive>
     }
   }
 
+  @override
+  void previsitDeferredAccess(ast.Send node, PrefixElement prefix, _) {
+    giveup(node, 'deferred access is not implemented');
+  }
+
   ir.Primitive visitNamedArgument(ast.NamedArgument node) {
     assert(irBuilder.isOpen);
     return visit(node.expression);