Remove support for 'argument definitions test' from dart2js.

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart b/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
index a15f5e00f55fe0af25c2619b144876434bec1982..61f6d847fb1da5aa06ee9302ae4955b058e80c02 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
@@ -976,10 +976,6 @@ class ConstantNamingVisitor implements ConstantVisitor {
     return constant.accept(this);
   }
 
-  visitSentinel(SentinelConstant constant) {
-    add(r'$');
-  }
-
   visitFunction(FunctionConstant constant) {
     add(constant.element.name.slowToString());
   }
@@ -1094,10 +1090,9 @@ class ConstantCanonicalHasher implements ConstantVisitor<int> {
     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());