function updatePageScaleFactor(finishCallback)
        {
            if (this._target && this._viewport) {
                var value = this._viewport.pageScaleFactor;
                value = increase ? value * 1.1 : value / 1.1;
                value = Math.min(this._viewport.maximumPageScaleFactor, value);
                value = Math.max(this._viewport.minimumPageScaleFactor, value)
                this._target.pageAgent().setPageScaleFactor(value);
            }
            finishCallback();
        }
@param {!WebInspector.Throttler.FinishCallback} finishCallback
@this {WebInspector.ResponsiveDesignView}