Only mark a proxy as bad if we have confirmation that another proxy succeeded for the same request.

net/proxy/proxy_service.h

 // Copyright (c) 2011 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_PROXY_PROXY_SERVICE_H_
 #define NET_PROXY_PROXY_SERVICE_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 79 matching lines @@
   //
   // Returns ERR_FAILED if there is not another proxy config to try.
   //
   // Profiling information for the request is saved to |net_log| if non-NULL.
   int ReconsiderProxyAfterError(const GURL& url,
                                 ProxyInfo* results,
                                 CompletionCallback* callback,
                                 PacRequest** pac_request,
                                 const BoundNetLog& net_log);
 
+  // Called to report that the last proxy connection succeeded.  If |proxy_info|
+  // has a non empty proxy_retry_info map, the proxies that have been tried (and
+  // failed) for this request will be marked as bad.
+  void ReportSuccess(const ProxyInfo& proxy_info);

[eroman, 2011/08/19 21:25:32]

We will need to be very careful to call this in all the right places. I wander
if there is any way to make this more future-proof (I can't think of anything
though).

+
   // Call this method with a non-null |pac_request| to cancel the PAC request.
   void CancelPacRequest(PacRequest* pac_request);
 
   // Sets the ProxyScriptFetcher and DhcpProxyScriptFetcher dependencies. This
   // is needed if the ProxyResolver is of type ProxyResolverWithoutFetch.
   // ProxyService takes ownership of both objects.
   void SetProxyScriptFetchers(
       ProxyScriptFetcher* proxy_script_fetcher,
       DhcpProxyScriptFetcher* dhcp_proxy_script_fetcher);
   ProxyScriptFetcher* GetProxyScriptFetcher() const;
@@ skipping 280 matching lines @@
 
   base::WaitableEvent event_;
   CompletionCallbackImpl<SyncProxyServiceHelper> callback_;
   ProxyInfo proxy_info_;
   int result_;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_SERVICE_H_