nsIPrefBranch *pBranch; nsresult     rv;
PR_AtomicIncrement(&g_InstanceCount); NS_INIT_REFCNT();
nsPref::nsPref()//----------------------------------------------------------------------------------------{  nsIPrefBranch *pBranch;  nsresult     rv;  PR_AtomicIncrement(&g_InstanceCount);  NS_INIT_REFCNT();  NS_WITH_SERVICE(nsIPrefService, pService, NS_PREFSERVICE_CONTRACTID, &rv);  mPrefService = pService;  mPrefService->GetDefaultBranch("", &pBranch);  mDefaultBranch = (nsIPrefBranch *)pBranch;}