Implement a 15 connection per proxy server limit.

net/http/http_network_transaction.h

Index: net/http/http_network_transaction.h
diff --git a/net/http/http_network_transaction.h b/net/http/http_network_transaction.h
index eb6f06ee91e0708da919aee2d25c0486c74d37f1..3217facc51c67b257e46e06cb3298faecea21599 100644
--- a/net/http/http_network_transaction.h
+++ b/net/http/http_network_transaction.h
@@ -362,9 +362,9 @@ class HttpNetworkTransaction : public HttpTransaction {
   // The next state in the state machine.
   State next_state_;
 
-  // The hostname and port of the peer.  This is not necessarily the one
-  // specified by the URL, due to Alternate-Protocol or proxies.
-  HostPortPair peer_;
+  // The hostname and port of the endpoint.  This is not necessarily the one
+  // specified by the URL, due to Alternate-Protocol or fixed testing ports.
+  HostPortPair endpoint_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpNetworkTransaction);
 };