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

net/proxy/proxy_info.cc

Index: net/proxy/proxy_info.cc
diff --git a/net/proxy/proxy_info.cc b/net/proxy/proxy_info.cc
index ebefa8463b025979deeecdce9b14f3227c612fe5..85d6caed1432f84c11983bf82d058fcfd2d98b4e 100644
--- a/net/proxy/proxy_info.cc
+++ b/net/proxy/proxy_info.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -16,26 +16,30 @@ ProxyInfo::~ProxyInfo() {
 
 void ProxyInfo::Use(const ProxyInfo& other) {
   proxy_list_ = other.proxy_list_;
+  proxy_retry_info_ = other.proxy_retry_info_;
 }
 
 void ProxyInfo::UseDirect() {
   proxy_list_.SetSingleProxyServer(ProxyServer::Direct());
+  proxy_retry_info_.clear();
 }
 
 void ProxyInfo::UseNamedProxy(const std::string& proxy_uri_list) {
   proxy_list_.Set(proxy_uri_list);
+  proxy_retry_info_.clear();
 }
 
 void ProxyInfo::UseProxyServer(const ProxyServer& proxy_server) {
   proxy_list_.SetSingleProxyServer(proxy_server);
+  proxy_retry_info_.clear();
 }
 
 std::string ProxyInfo::ToPacString() const {
   return proxy_list_.ToPacString();
 }
 
-bool ProxyInfo::Fallback(ProxyRetryInfoMap* proxy_retry_info) {
-  return proxy_list_.Fallback(proxy_retry_info);
+bool ProxyInfo::Fallback(const BoundNetLog& net_log) {
+  return proxy_list_.Fallback(&proxy_retry_info_, net_log);
 }
 
 void ProxyInfo::DeprioritizeBadProxies(