Allow ProxyConfigService to report "no configuration set"

net/proxy/proxy_config_service_mac.h

Index: net/proxy/proxy_config_service_mac.h
diff --git a/net/proxy/proxy_config_service_mac.h b/net/proxy/proxy_config_service_mac.h
index 68a7d22aed09c3417fdc18b72524eda6b062faad..3625c398c380d1198ebf95e570526e05c9e477a7 100644
--- a/net/proxy/proxy_config_service_mac.h
+++ b/net/proxy/proxy_config_service_mac.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 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.
 
@@ -27,7 +27,7 @@ class ProxyConfigServiceMac : public ProxyConfigService {
   // ProxyConfigService implementation:
   virtual void AddObserver(Observer* observer);
   virtual void RemoveObserver(Observer* observer);
-  virtual bool GetLatestProxyConfig(ProxyConfig* config);
+  virtual ConfigAvailability GetLatestProxyConfig(ProxyConfig* config);
 
  private:
   class Helper;