src/vs/workbench/services/workingCopy/electron-sandbox/workingCopyBackupTracker.ts/NativeWorkingCopyBackupTracker/onBeforeShutdown
class NativeWorkingCopyBackupTracker:	protected onBeforeShutdown(reason: ShutdownReason): boolean | Promise<boolean> {

		// Dirty working copies need treatment on shutdown
		const dirtyWorkingCopies = this.workingCopyService.dirtyWorkingCopies;
		if (dirtyWorkingCopies.length) {
			return this.onBeforeShutdownWithDirty(reason, dirtyWorkingCopies);
		}

		// No dirty working copies
		return this.onBeforeShutdownWithoutDirty();
	}