Allow ProxyConfigService to report "no configuration set"

net/proxy/polling_proxy_config_service.h

Index: net/proxy/polling_proxy_config_service.h
diff --git a/net/proxy/polling_proxy_config_service.h b/net/proxy/polling_proxy_config_service.h
index b4295ec10344d69f776b4eb4a4e405c1f5eca221..dd65ac2fd3ff82fea8e57c64c880f92da193632b 100644
--- a/net/proxy/polling_proxy_config_service.h
+++ b/net/proxy/polling_proxy_config_service.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 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.
 
@@ -6,8 +6,8 @@
 #define NET_PROXY_POLLING_PROXY_CONFIG_SERVICE_H_
 #pragma once
 
-#include "base/time.h"
 #include "base/ref_counted.h"
+#include "base/time.h"
 #include "net/proxy/proxy_config_service.h"
 
 namespace net {
@@ -22,14 +22,15 @@ class PollingProxyConfigService : public ProxyConfigService {
   // ProxyConfigService implementation:
   virtual void AddObserver(Observer* observer);
   virtual void RemoveObserver(Observer* observer);
-  virtual bool GetLatestProxyConfig(ProxyConfig* config);
+  virtual ConfigAvailability GetLatestProxyConfig(ProxyConfig* config);
   virtual void OnLazyPoll();
 
  protected:
   // Function for retrieving the current proxy configuration.
   // Implementors must be threadsafe as the function will be invoked from
   // worker threads.
-  typedef void (*GetConfigFunction)(ProxyConfig*);
+  typedef ProxyConfigService::ConfigAvailability
+      (*GetConfigFunction)(ProxyConfig*);
 
   // Creates a polling-based ProxyConfigService which will test for new
   // settings at most every |poll_interval| time by calling |get_config_func|