Remove support for 'argument definitions test' from dart2js.

sdk/lib/_internal/compiler/implementation/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer implements ClosureNamer {
@@ skipping 958 matching lines @@
       add(fragment);
     } else {
       failed = true;
     }
   }
 
   _visit(Constant constant) {
     return constant.accept(this);
   }
 
-  visitSentinel(SentinelConstant constant) {
-    add(r'$');
-  }
-
   visitFunction(FunctionConstant constant) {
     add(constant.element.name.slowToString());
   }
 
   visitNull(NullConstant constant) {
     add('null');
   }
 
   visitInt(IntConstant constant) {
     // No `addRoot` since IntConstants are always inlined.
@@ skipping 94 matching lines @@
 
   int _visit(Constant constant) {
     int hash = hashes[constant];
     if (hash == null) {
       hash = _finish(constant.accept(this));
       hashes[constant] = hash;
     }
     return hash;
   }
 
-  int visitSentinel(SentinelConstant constant) => 1;
-  int visitNull(NullConstant constant) => 2;
-  int visitTrue(TrueConstant constant) => 3;
-  int visitFalse(FalseConstant constant) => 4;
+  int visitNull(NullConstant constant) => 1;
+  int visitTrue(TrueConstant constant) => 2;
+  int visitFalse(FalseConstant constant) => 3;
 
   int visitFunction(FunctionConstant constant) {
     return _hashString(1, constant.element.name.slowToString());
   }
 
   int visitInt(IntConstant constant) => _hashInt(constant.value);
 
   int visitDouble(DoubleConstant constant) => _hashDouble(constant.value);
 
   int visitString(StringConstant constant) {
@@ skipping 144 matching lines @@
         if (!first) {
           sb.write('_');
         }
         sb.write('_');
         visit(link.head);
         first = true;
       }
     }
   }
 }