src/vs/workbench/browser/layout.ts/Layout/offset
class Layout:	get offset() {
		return {
			top: (() => {
				let offset = 0;
				if (this.isVisible(Parts.TITLEBAR_PART)) {
					offset = this.getPart(Parts.TITLEBAR_PART).maximumHeight;
				}

				return offset;
			})()
		};
	}