src/vs/workbench/browser/parts/panel/panelPart.ts/PanelPart/getToolbarWidth
class PanelPart:	private getToolbarWidth(): number {
		const activePanel = this.getActivePanel();
		if (!activePanel || !this.toolBar) {
			return 0;
		}

		return this.toolBar.getItemsWidth();
	}