src/vs/workbench/services/workingCopy/common/workingCopyBackupTracker.ts/WorkingCopyBackupTracker/onDidUnregister
class WorkingCopyBackupTracker:	private onDidUnregister(workingCopy: IWorkingCopy): void {

		// Remove from content version map
		this.mapWorkingCopyToContentVersion.delete(workingCopy);

		// Check suspended
		if (this.suspended) {
			this.logService.warn(`[backup tracker] suspended, ignoring unregister event`, workingCopy.resource.toString(), workingCopy.typeId);
			return;
		}

		// Discard backup
		this.discardBackup(workingCopy);
	}