Reapply "reflectType() dynamic type arguments support (#26012)"

pkg/compiler/lib/src/js_backend/backend.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.
 
 library js_backend.backend;
 
 import 'dart:async' show Future;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
 
@@ skipping 1969 matching lines @@
   bool isAccessibleByReflection(Element element) {
     if (element.isClass) {
       element = getDartClass(element);
     }
     return membersNeededForReflection.contains(element);
   }
 
   /**
    * Returns true if the element has to be resolved due to a mirrorsUsed
    * annotation. If we have insufficient mirrors used annotations, we only
-   * keep additonal elements if treeshaking has been disabled.
+   * keep additional elements if treeshaking has been disabled.
    */
   bool requiredByMirrorSystem(Element element) {
     return hasInsufficientMirrorsUsed && isTreeShakingDisabled ||
         matchesMirrorsMetaTarget(element) ||
         targetsUsed.contains(element);
   }
 
   /**
    * Returns true if the element matches a mirrorsUsed annotation. If
    * we have insufficient mirrorsUsed information, this returns true for
@@ skipping 1276 matching lines @@
   @override
   bool isNativeClass(ClassElement element) {
     return helpers.backend.isNative(element);
   }
 
   @override
   bool isNativeMember(MemberElement element) {
     return helpers.backend.isNative(element);
   }
 }