Shorter encoding for zero optional arguments.

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Review URL: https://codereview.chromium.org/2092243002 .

Addresses: #26754

Author: rakudrama

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

@@ -833,6 +833,9 @@ class FragmentEmitter {
     // TODO(herhut): Replace [js.LiteralNull] with [js.ArrayHole].
     if (method.optionalParameterDefaultValues is List) {
       List<ConstantValue> defaultValues = method.optionalParameterDefaultValues;
+      if (defaultValues.isEmpty) {
+        return new js.LiteralNull();
+      }
       Iterable<js.Expression> elements =
           defaultValues.map(generateConstantReference);
       return js.js('function() { return #; }',

sdk/lib/_internal/js_runtime/lib/js_helper.dart

@@ -1369,6 +1369,11 @@ class Primitives {
     }
 
     if (!acceptsOptionalArguments) {
+      if (namedArguments != null && namedArguments.isNotEmpty) {
+        // Tried to invoke a function that takes a fixed number of arguments
+        // with named (optional) arguments.
+        return functionNoSuchMethod(function, arguments, namedArguments);
+      }
       if (argumentCount == requiredParameterCount) {
         return JS('var', r'#.apply(#, #)', jsFunction, function, arguments);
       }