Add support for parsing, but not capturing, assers in constructor initializer lists

pkg/analyzer/test/generated/parser_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 analyzer.test.generated.parser_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/src/dart/ast/token.dart';
@@ skipping 7076 matching lines @@
   }
 
   void test_parseConstructor() {
     // TODO(brianwilkerson) Implement tests for this method.
 //    parse("parseConstructor", new Class[] {Parser.CommentAndMetadata.class,
 //        Token.class, Token.class, SimpleIdentifier.class, Token.class,
 //        SimpleIdentifier.class, FormalParameterList.class}, new Object[] {emptyCommentAndMetadata(),
 //        null, null, null, null, null, null}, "");
   }
 
+  void test_parseConstructor_assert() {
+    ClassMember classMember = parse("parseClassMember", <Object>["C"],
+        "C(x, y) : _x = x, assert (x < y), _y = y;");
+    expect(classMember, new isInstanceOf<ConstructorDeclaration>());
+    ConstructorDeclaration constructor = classMember as ConstructorDeclaration;
+    NodeList<ConstructorInitializer> initializers = constructor.initializers;
+    expect(initializers, hasLength(2));
+  }
+
   void test_parseConstructor_with_pseudo_function_literal() {
     // "(b) {}" should not be misinterpreted as a function literal even though
     // it looks like one.
     ClassMember classMember =
         parse("parseClassMember", <Object>["C"], "C() : a = (b) {}");
     EngineTestCase.assertInstanceOf((obj) => obj is ConstructorDeclaration,
         ConstructorDeclaration, classMember);
     ConstructorDeclaration constructor = classMember as ConstructorDeclaration;
     NodeList<ConstructorInitializer> initializers = constructor.initializers;
     expect(initializers, hasLength(1));
@@ skipping 4223 matching lines @@
         new Scanner(null, new CharSequenceReader(source), listener);
     Token tokenStream = scanner.tokenize();
     //
     // Parse the source.
     //
     Parser parser = new Parser(null, listener);
     return invokeParserMethodImpl(
         parser, methodName, <Object>[tokenStream], tokenStream) as Token;
   }
 }