code: protected void initializePortletWindowData(
              HttpServletRequest request, PortletWindowData portletWindowData) {
          final IStylesheetDescriptor stylesheetDescriptor = getThemeStylesheetDescriptor(request);
          final IPortletEntityId portletEntityId = portletWindowData.getPortletEntityId();
          final IPortletEntity portletEntity =
                  this.portletEntityRegistry.getPortletEntity(request, portletEntityId);
          final WindowState entityWindowState = portletEntity.getWindowState(stylesheetDescriptor);
          if (persistentWindowStates.contains(entityWindowState)) {
              portletWindowData.setWindowState(entityWindowState);
          } else if (entityWindowState != null) {
              // Set of persistent window states must have changed, nuke the old value
              this.logger.warn(
                      "PortletEntity.windowState="
                              + entityWindowState
                              + " but that state is not in the set of persistent WindowStates. PortletEntity.windowState will be set to null");
              portletEntity.setWindowState(stylesheetDescriptor, null);
              this.portletEntityRegistry.storePortletEntity(request, portletEntity);
          }
      }
docs: Initializes a newly created {@link PortletWindow}, the default implementation sets up the
  appropriate {@link WindowState} and {@link javax.portlet.PortletMode}