Race TCP connection to proxies with QUIC connections

net/base/proxy_delegate.h

Index: net/base/proxy_delegate.h
diff --git a/net/base/proxy_delegate.h b/net/base/proxy_delegate.h
index ab6b2445f54bb3a4005a43b137e13110496ff5ee..0ebc3261b1540a59cf98b4792a6f581ff6739d62 100644
--- a/net/base/proxy_delegate.h
+++ b/net/base/proxy_delegate.h
@@ -68,6 +68,21 @@ class NET_EXPORT ProxyDelegate {
   // 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);
 };