Bug 1420677 - Make sure to update addr_info_gencnt each time we change addr_info r=dragana

When changing addr_info we didn't always update addr_info_gencnt, so when it the old AddrInfo was freed, even though we lock in nsDNSRecord::GetNextAddr, mIter would still point to the old AddrInfo.

Differential Revision: https://phabricator.services.mozilla.com/D23923

--HG--
extra : moz-landing-system : lando

netwerk/dns/nsHostResolver.cpp

@@ -1009,6 +1009,7 @@ nsresult nsHostResolver::ResolveHost(const nsACString &aHost, uint16_t type,
             MutexAutoLock lock(addrRec->addr_info_lock);
 
             addrRec->addr_info = nullptr;
+            addrRec->addr_info_gencnt++;
             if (unspecRec->negative) {
               rec->negative = unspecRec->negative;
               rec->CopyExpirationTimesAndFlagsFrom(unspecRec);
@@ -1026,6 +1027,7 @@ nsresult nsHostResolver::ResolveHost(const nsACString &aHost, uint16_t type,
                         new AddrInfo(addrUnspecRec->addr_info->mHostName,
                                      addrUnspecRec->addr_info->mCanonicalName,
                                      addrUnspecRec->addr_info->IsTRR());
+                    addrRec->addr_info_gencnt++;
                     rec->CopyExpirationTimesAndFlagsFrom(unspecRec);
                   }
                   addrRec->addr_info->AddAddress(new NetAddrElement(*addrIter));