function categoryBand(category)
        {
            var categories = WebInspector.TimelineUIUtils.NetworkCategory;
            switch (category) {
            case categories.HTML: return 0;
            case categories.Script: return 1;
            case categories.Style: return 2;
            case categories.Media: return 3;
            default: return 4;
            }
        }
@param {!WebInspector.TimelineUIUtils.NetworkCategory} category
@return {number}