The size of the element.

def size(self):
        """The size of the element."""
        size = {}
        if self._w3c:
            size = self._execute(Command.GET_ELEMENT_RECT)['value']
        else:
            size = self._execute(Command.GET_ELEMENT_SIZE)['value']
        new_size = {"height": size["height"],
                    "width": size["width"]}
        return new_size