function maybeShowPopover(fragment)
        {
            if (!fragment.firstChild)
                return;
            var content = new WebInspector.TimelineOverviewPane.PopoverContents();
            this._popoverContents = content.contentElement.createChild("div");
            this._popoverContents.appendChild(fragment);
            this._popover = popover;
            popover.showView(content, this._cursorElement);
        }
@this {WebInspector.TimelineOverviewPane}
@param {!DocumentFragment} fragment