bug 1503393 - never let "localhost" get sent to a proxy r=mayhemer

netwerk/base/nsProtocolProxyService.cpp

@@ -2032,6 +2032,12 @@ nsresult nsProtocolProxyService::Resolve_Internal(nsIChannel *channel,
   // here means that we will not use a proxy for this connection.
   if (mPACMan && mPACMan->IsPACURI(uri)) return NS_OK;
 
+  // if proxies are enabled and this host:port combo is supposed to use a
+  // proxy, check for a proxy.
+  if ((mProxyConfig == PROXYCONFIG_DIRECT) ||
+      !CanUseProxy(uri, info.defaultPort))
+    return NS_OK;
+
   bool mainThreadOnly;
   if (mSystemProxySettings && mProxyConfig == PROXYCONFIG_SYSTEM &&
       NS_SUCCEEDED(mSystemProxySettings->GetMainThreadOnly(&mainThreadOnly)) &&