src/vs/base/browser/ui/grid/grid.ts/Grid/addView
class Grid:	addView(newView: T, size: number | Sizing, referenceView: T, direction: Direction): void {
		if (this.views.has(newView)) {
			throw new Error('Can\'t add same view twice');
		}

		const orientation = getDirectionOrientation(direction);

		if (this.views.size === 1 && this.orientation !== orientation) {
			this.orientation = orientation;
		}

		const referenceLocation = this.getViewLocation(referenceView);
		const location = getRelativeLocation(this.gridview.orientation, referenceLocation, direction);

		let viewSize: number | GridViewSizing;

		if (typeof size === 'number') {
			viewSize = size;
		} else if (size.type === 'split') {
			const [, index] = tail(referenceLocation);
			viewSize = GridViewSizing.Split(index);
		} else if (size.type === 'distribute') {
			viewSize = GridViewSizing.Distribute;
		} else {
			viewSize = size;
		}

		this._addView(newView, viewSize, location);
	}