code: public Rectangle getViewport() {
  		@SuppressWarnings("unchecked")
  		Map<String, Number> result = (Map<String, Number>) executeScript(JS_GET_VIEWPORT);
  		int width = result.get("width").intValue();
  		int height = result.get("height").intValue();
  		Rectangle viewport = new Rectangle(0, 0, height, width, width, height);
  		LOGGER.info("Viewport rectangle: {}", viewport);
  		return viewport;
  	}
docs: Returns the size of the viewport excluding, if rendered, the vertical and horizontal scrollbars.
  Uses JavaScript calling document.documentElement.client[Width|Height]().
  
  @return the rectangle