Bypass data reduction proxy if no handler is found for a 407 error.

net/proxy/proxy_service.h

Index: net/proxy/proxy_service.h
diff --git a/net/proxy/proxy_service.h b/net/proxy/proxy_service.h
index 6f8556879f67fb00fe28bdaa312a0a5bd81c7926..269f1c04522119397f1ce49e7d80e1a16594706d 100644
--- a/net/proxy/proxy_service.h
+++ b/net/proxy/proxy_service.h
@@ -292,6 +292,9 @@ class NET_EXPORT ProxyService : public NetworkChangeNotifier::IPAddressObserver,
     // Bypass the proxy because the proxy, not the origin, sent a 4xx response.
     PROXY_4XX_BYPASS,
 
+    // Bypass the proxy because we got a 407 from the proxy without a challenge.
+    MALFORMED_407_BYPASS,
+
     // This must always be last.
     BYPASS_EVENT_TYPE_MAX
   };