reapply r70628. It was wrongly blamed for breaking Linux valgrind bots.

net/http/http_network_session.h

Index: net/http/http_network_session.h
diff --git a/net/http/http_network_session.h b/net/http/http_network_session.h
index 5a3b96ccfe5849a2069717f13daea513b2688c9f..b36d7f7146a3b851b4e737797a45a9661eb2119f 100644
--- a/net/http/http_network_session.h
+++ b/net/http/http_network_session.h
@@ -130,6 +130,10 @@ class HttpNetworkSession : public base::RefCounted<HttpNetworkSession>,
     return &http_stream_factory_;
   }
 
+  NetLog* net_log() {
+    return net_log_;
+  }
+
   // Creates a Value summary of the state of the socket pools. The caller is
   // responsible for deleting the returned value.
   Value* SocketPoolInfoToValue() const {