src/vs/platform/windows/electron-main/windowsMainService.ts/WindowsMainService/doOpenFilesInExistingWindow
class WindowsMainService:	private doOpenFilesInExistingWindow(configuration: IOpenConfiguration, window: ICodeWindow, filesToOpen?: IFilesToOpen): ICodeWindow {
		this.logService.trace('windowsManager#doOpenFilesInExistingWindow');

		window.focus(); // make sure window has focus

		const params: INativeOpenFileRequest = {
			filesToOpenOrCreate: filesToOpen?.filesToOpenOrCreate,
			filesToDiff: filesToOpen?.filesToDiff,
			filesToWait: filesToOpen?.filesToWait,
			termProgram: configuration?.userEnv?.['TERM_PROGRAM']
		};
		window.sendWhenReady('vscode:openFiles', CancellationToken.None, params);

		return window;
	}