src/vs/editor/contrib/dropIntoEditor/browser/dropIntoEditorContribution.ts/DropIntoEditorController/extractDataTransferData
class DropIntoEditorController:	public async extractDataTransferData(dragEvent: DragEvent): Promise<VSDataTransfer> {
		if (!dragEvent.dataTransfer) {
			return new VSDataTransfer();
		}

		const textEditorDataTransfer = toVSDataTransfer(dragEvent.dataTransfer);
		addExternalEditorsDropData(textEditorDataTransfer, dragEvent);
		return textEditorDataTransfer;
	}