Remove support for 'argument definitions test' from dart2js.

sdk/lib/_internal/compiler/implementation/constants.dart

 // Copyright (c) 2012, 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.
 
 part of dart2js;
 
 abstract class ConstantVisitor<R> {
-  R visitSentinel(SentinelConstant constant);
   R visitFunction(FunctionConstant constant);
   R visitNull(NullConstant constant);
   R visitInt(IntConstant constant);
   R visitDouble(DoubleConstant constant);
   R visitTrue(TrueConstant constant);
   R visitFalse(FalseConstant constant);
   R visitString(StringConstant constant);
   R visitList(ListConstant constant);
   R visitMap(MapConstant constant);
   R visitConstructed(ConstructedConstant constant);
@@ skipping 27 matching lines @@
   bool isNaN() => false;
   bool isMinusZero() => false;
 
   DartType computeType(Compiler compiler);
 
   List<Constant> getDependencies();
 
   accept(ConstantVisitor visitor);
 }
 
-class SentinelConstant extends Constant {
-  const SentinelConstant();
-  static final SENTINEL = const SentinelConstant();
-
-  List<Constant> getDependencies() => const <Constant>[];
-
-  // Just use a random value.
-  int get hashCode => 24297418;
-
-  bool isSentinel() => true;
-
-  accept(ConstantVisitor visitor) => visitor.visitSentinel(this);
-
-  DartType computeType(Compiler compiler) => compiler.types.dynamicType;
-}
-
 class FunctionConstant extends Constant {
   Element element;
 
   FunctionConstant(this.element);
 
   bool isFunction() => true;
 
   bool operator ==(var other) {
     if (other is !FunctionConstant) return false;
     return identical(other.element, element);
@@ skipping 412 matching lines @@
     for (int i = 0; i < fields.length; i++) {
       if (fields[i] != other.fields[i]) return false;
     }
     return true;
   }
 
   List<Constant> getDependencies() => fields;
 
   accept(ConstantVisitor visitor) => visitor.visitConstructed(this);
 }