function callback(error, payload)
        {
            this._cssModel._pendingCommandsMajorState.pop();
            if (!userCallback)
                return;

            if (error) {
                console.error(error);
                userCallback(null);
            } else
                userCallback(WebInspector.CSSStyleDeclaration.parsePayload(this._cssModel, payload));
        }
@param {?string} error
@param {!CSSAgent.CSSStyle} payload
@this {!WebInspector.CSSStyleDeclaration}