Enable messages in asserts by default

pkg/analyzer/lib/src/error/codes.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.src.error.codes;
 
 import 'package:analyzer/error/error.dart';
 
 export 'package:analyzer/src/analysis_options/error/option_codes.dart';
 export 'package:analyzer/src/dart/error/hint_codes.dart';
@@ skipping 935 matching lines @@
    * See [IMPLEMENTS_DEFERRED_CLASS], and [MIXIN_DEFERRED_CLASS].
    */
   static const CompileTimeErrorCode EXTENDS_DEFERRED_CLASS =
       const CompileTimeErrorCode(
           'EXTENDS_DEFERRED_CLASS',
           "This class can't extend the deferred class '{0}'.",
           "Try specifying a different superclass, or "
           "removing the extends clause.");
 
   /**
-   * DEP 37 extends the syntax for assert() to allow a second "message"
-   * argument.  We issue this error if the user tries to supply a "message"
-   * argument but the DEP is not enabled.
-   */
-  static const CompileTimeErrorCode EXTRA_ARGUMENT_TO_ASSERT =
-      const CompileTimeErrorCode(
-          'EXTRA_ARGUMENT_TO_ASSERT',
-          "Assertions only accept a single argument.",
-          "Try removing the message, or enable messages in assert statements.");
-
-  /**
    * 12.14.2 Binding Actuals to Formals: It is a static warning if <i>m &lt;
    * h</i> or if <i>m &gt; n</i>.
    *
    * 16.12.2 Const: It is a compile-time error if evaluation of a constant
    * object results in an uncaught exception being thrown.
    *
    * Parameters:
    * 0: the maximum number of positional arguments
    * 1: the actual number of positional arguments given
    */
@@ skipping 3939 matching lines @@
    * created from the optional [correction] template.
    */
   const StrongModeCode(ErrorType type, String name, String message,
       [String correction])
       : type = type,
         super('STRONG_MODE_$name', message, correction);
 
   @override
   ErrorSeverity get errorSeverity => type.severity;
 }