src/vs/base/browser/ui/splitview/paneview.ts/PaneDraggable/onDrop
class PaneDraggable:	private onDrop(e: DragEvent): void {
		if (!this.context.draggable) {
			return;
		}

		EventHelper.stop(e);

		this.dragOverCounter = 0;
		this.render();

		if (this.dnd.canDrop(this.context.draggable.pane, this.pane) && this.context.draggable !== this) {
			this._onDidDrop.fire({ from: this.context.draggable.pane, to: this.pane });
		}

		this.context.draggable = null;
	}