src/vs/workbench/contrib/files/browser/views/openEditorsView.ts/OpenEditorsDragAndDrop/onDragStart
class OpenEditorsDragAndDrop:	onDragStart(data: IDragAndDropData, originalEvent: DragEvent): void {
		const items = (data as ElementsDragAndDropData<OpenEditor | IEditorGroup>).elements;
		const editors: IEditorIdentifier[] = [];
		if (items) {
			for (const item of items) {
				if (item instanceof OpenEditor) {
					editors.push(item);
				}
			}
		}

		if (editors.length) {
			// Apply some datatransfer types to allow for dragging the element outside of the application
			this.instantiationService.invokeFunction(fillEditorsDragData, editors, originalEvent);
		}
	}