Fix bot failure because of missed update of AssertStatement

pkg/analyzer/lib/src/kernel/ast_from_analyzer.dart

 // Copyright (c) 2016, 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.
 library kernel.analyzer.ast_from_analyzer;
 
 import 'package:kernel/ast.dart' as ast;
 import 'package:kernel/frontend/super_initializers.dart';
 import 'package:kernel/log.dart';
 import 'package:kernel/type_algebra.dart';
 import 'package:kernel/transformations/flags.dart';
@@ skipping 981 matching lines @@
   LabelStack findLabelTarget(String label, LabelStack stack) {
     while (stack != null) {
       if (stack.labels.contains(label)) return stack;
       stack = stack.next;
     }
     return null;
   }
 
   ast.Statement visitAssertStatement(AssertStatement node) {
     return new ast.AssertStatement(scope.buildExpression(node.condition),
-        scope.buildOptionalExpression(node.message));
+        message: scope.buildOptionalExpression(node.message));
   }
 
   ast.Statement visitBlock(Block node) {
     List<ast.Statement> statements = <ast.Statement>[];
     for (Statement statement in node.statements) {
       buildBlockMember(statement, statements);
     }
     return new ast.Block(statements);
   }
 
@@ skipping 2074 matching lines @@
     if (list[i - 1].compareTo(item) == 0) {
       ++deleted;
     } else if (deleted > 0) {
       list[i - deleted] = item;
     }
   }
   if (deleted > 0) {
     list.length -= deleted;
   }
 }