docs: static Scriptable checkDynamicScope(Scriptable possibleDynamicScope,
                                          Scriptable staticTopScope)
      {
          // Return cx.topCallScope if scope
          if (possibleDynamicScope == staticTopScope) {
              return possibleDynamicScope;
          }
          Scriptable proto = possibleDynamicScope;
          for (;;) {
              proto = proto.getPrototype();
              if (proto == staticTopScope) {
                  return possibleDynamicScope;
              }
              if (proto == null) {
                  return staticTopScope;
              }
          }
      }