Add support for assert statements with messages to the analyzer.

pkg/analyzer/test/generated/ast_test.dart

 // Copyright (c) 2014, 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 engine.ast_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/java_engine.dart' show Predicate;
 import 'package:analyzer/src/generated/java_engine.dart';
@@ skipping 1670 matching lines @@
         "e as T",
         AstFactory.asExpression(
             AstFactory.identifier3("e"), AstFactory.typeName4("T")));
   }
 
   void test_visitAssertStatement() {
     _assertSource(
         "assert (a);", AstFactory.assertStatement(AstFactory.identifier3("a")));
   }
 
+  void test_visitAssertStatement_withMessage() {
+    _assertSource(
+        "assert (a, b);",
+        AstFactory.assertStatement(
+            AstFactory.identifier3("a"), AstFactory.identifier3('b')));
+  }
+
   void test_visitAssignmentExpression() {
     _assertSource(
         "a = b",
         AstFactory.assignmentExpression(AstFactory.identifier3("a"),
             TokenType.EQ, AstFactory.identifier3("b")));
   }
 
   void test_visitAwaitExpression() {
     _assertSource(
         "await e;", AstFactory.awaitExpression(AstFactory.identifier3("e")));
@@ skipping 2193 matching lines @@
   static const List<WrapperKind> values = const [
     PREFIXED_LEFT,
     PREFIXED_RIGHT,
     PROPERTY_LEFT,
     PROPERTY_RIGHT,
     NONE
   ];
 
   const WrapperKind(String name, int ordinal) : super(name, ordinal);
 }