Race TCP connection to proxies with QUIC connections

net/base/proxy_delegate.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_BASE_PROXY_DELEGATE_H_
 #define NET_BASE_PROXY_DELEGATE_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 50 matching lines @@
   // Called after the response headers for the tunnel request are received.
   virtual void OnTunnelHeadersReceived(
       const HostPortPair& origin,
       const HostPortPair& proxy_server,
       const HttpResponseHeaders& response_headers) = 0;
 
   // Returns true if |proxy_server| is a trusted SPDY/HTTP2 proxy that is
   // allowed to push cross-origin resources.
   virtual bool IsTrustedSpdyProxy(const net::ProxyServer& proxy_server) = 0;
 
+  // Called after the proxy is resolved but before the connection is
+  // established. |resolved_proxy_server| is the proxy server resolved by the
+  // proxy service for fetching |url|. Sets |alternative_proxy_server| to an
+  // alternative proxy server, if one is available to fetch |url|.
+  // |alternative_proxy_server| is owned by the caller, and is guaranteed to be
+  // non-null.
+  virtual void GetAlternativeProxy(
+      const GURL& url,
+      const ProxyServer& resolved_proxy_server,
+      ProxyServer* alternative_proxy_server) const {}

[Ryan Hamilton, 2016/08/25 18:39:28]

nit: The other methods in this class are pure so I think these should probably
be so as well.

[tbansal1, 2016/08/25 18:42:02]

Is it okay if I change the other methods to be not-pure (in a different CL)? It
would reduce the overhead of adding empty implementations of the method at 3-4
different places. (But, I am okay with whatever you suggest finally.)

[Ryan Hamilton, 2016/08/25 18:50:26]

I think it's best to do it now because it forces us to look at those call sites
and make sure they don't actually need to do something. (I'm 99% sure they
don't, but it'd be worth looking at them to make sure)

Sorry for the added headache!

[tbansal1, 2016/08/25 20:20:19]

Going with your first suggestion of changing them to pure virtual to be
consistent with other functions.

+
+  // Notifies the ProxyDelegate that |alternative_proxy_server| is broken.
+  virtual void OnAlternativeProxyBroken(
+      const ProxyServer& alternative_proxy_server) {}
+
  private:
   DISALLOW_COPY_AND_ASSIGN(ProxyDelegate);
 };
 
 }
 
 #endif  // NET_BASE_PROXY_DELEGATE_H_