[strong] weak classes can't inherit from strong ones

test/mjsunit/strong/class-object-frozen.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --strong-mode
 
 "use strict";
 
 function getClass() {
   class Foo {
@@ skipping 61 matching lines @@
       static get bar() { return 0 }
       get bar() { return 0 }
     }
     return Foo;
   }
 
   testStrongClass(classFunc);
   assertDoesNotThrow(function(){addProperty(parent)});
   assertDoesNotThrow(function(){convertPropertyToData(parent)});
 })();
-
-// Check strong classes don't freeze their children.
-(function() {
-  let parent = getClassStrong();
-
-  let classFunc = function() {
-    class Foo extends parent {
-      static get bar() { return 0 }
-      get bar() { return 0 }
-    }
-    return Foo;
-  }
-
-  assertThrows(function(){addProperty(parent)}, TypeError);
-  assertThrows(function(){convertPropertyToData(parent)}, TypeError);
-  testWeakClass(classFunc);
-})();