'Updates self.properties, if Properties has changed.
If Properties has changed, update self.properties, so we
get the new values during any subsequent adjustment.'

def handle_update(self, json_snippet, tmpl_diff, prop_diff):

    if tmpl_diff:
        if tmpl_diff.update_policy_changed():
            up = json_snippet.update_policy(self.update_policy_schema, self.context)
            self.update_policy = up
    self.properties = json_snippet.properties(self.properties_schema, self.context)
    if prop_diff:
        self._try_rolling_update(prop_diff)
    if (self.properties[self.SIZE] is not None):
        self.resize(self.properties[self.SIZE])
    else:
        curr_size = grouputils.get_size(self)
        self.resize(curr_size)
