Remove support for 'argument definitions test' from dart2js.

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index 0a2f53a33bf9c4250acb93fc0c858034119eda4d..e502f250bf7fed1141a5ba8c4230a62406e86f1d 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -1009,9 +1009,6 @@ class CodeEmitterTask extends CompilerTask {
           argumentsBuffer[count] = js(jsName);
           parametersBuffer[optionalParameterStart + index] =
               new jsAst.Parameter(jsName);
-        // Note that [elements] may be null for a synthesized [member].
-        } else if (elements != null && elements.isParameterChecked(element)) {
-          argumentsBuffer[count] = constantReference(SentinelConstant.SENTINEL);
         } else {
           Constant value = handler.initialVariableValues[element];
           if (value == null) {