Add optional message to assert in Dart2js.

pkg/compiler/lib/src/resolution/send_structure.dart

 // Copyright (c) 2015, 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 dart2js.resolution.send_structure;
 
 import '../dart_types.dart';
 import '../diagnostics/spannable.dart' show
     SpannableAssertionFailure;
 import '../constants/expressions.dart';
@@ skipping 14 matching lines @@
 
 /// Interface for the structure of the semantics of a [Send] node.
 ///
 /// Subclasses handle each of the [Send] variations; `assert(e)`, `a && b`,
 /// `a.b`, `a.b(c)`, etc.
 abstract class SendStructure<R, A> extends SemanticSendStructure<R, A> {
   /// Calls the matching visit method on [visitor] with [send] and [arg].
   R dispatch(SemanticSendVisitor<R, A> visitor, Send send, A arg);
 }
 
-/// The structure for a [Send] of the form `assert(e)`.
-class AssertStructure<R, A> implements SendStructure<R, A> {
-  const AssertStructure();
-
-  R dispatch(SemanticSendVisitor<R, A> visitor, Send node, A arg) {
-    return visitor.visitAssert(
-        node,
-        node.arguments.single,
-        arg);
-  }
-
-  String toString() => 'assert';
-}
-
-/// The structure for a [Send] of the form an `assert` with less or more than
-/// one argument.
-class InvalidAssertStructure<R, A> implements SendStructure<R, A> {
-  const InvalidAssertStructure();
-
-  R dispatch(SemanticSendVisitor<R, A> visitor, Send node, A arg) {
-    return visitor.errorInvalidAssert(
-        node,
-        node.argumentsNode,
-        arg);
-  }
-
-  String toString() => 'invalid assert';
-}
-
 /// The structure for a [Send] of the form `a ?? b`.
 class IfNullStructure<R, A> implements SendStructure<R, A> {
   const IfNullStructure();
 
   R dispatch(SemanticSendVisitor<R, A> visitor, Send node, A arg) {
     return visitor.visitIfNull(
         node,
         node.receiver,
         node.arguments.single,
         arg);
@@ skipping 2902 matching lines @@
   ThisConstructorInvokeStructure(
       this.node, this.constructor, this.callStructure);
 
   R dispatch(SemanticDeclarationVisitor<R, A> visitor, A arg) {
     return visitor.visitThisConstructorInvoke(
         node, constructor, node.argumentsNode, callStructure, arg);
   }
 
   bool get isConstructorInvoke => true;
 }