Allow ProxyConfigService to report "no configuration set"

net/proxy/proxy_config_service.h

Index: net/proxy/proxy_config_service.h
diff --git a/net/proxy/proxy_config_service.h b/net/proxy/proxy_config_service.h
index da67cd67130d27f8786501d272600644312684b5..aa2d848923220b0b4e17003afb76d13535f0c98b 100644
--- a/net/proxy/proxy_config_service.h
+++ b/net/proxy/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.
 
@@ -13,11 +13,22 @@ class ProxyConfig;
 // Service for watching when the proxy settings have changed.
 class ProxyConfigService {
  public:
+  // Indicates whether proxy configuration is valid, and if not, why.
+  enum ConfigAvailability {
+    // Configuration is pending, observers will be notified later.
+    CONFIG_PENDING,
+    // Configuration is present and valid.
+    CONFIG_VALID,
+    // No configuration is set, use default.

[eroman, 2011/03/16 01:30:00]

nit: I suggest removing the "use default" comment (it is up to the caller to
decide what they want to do).

[Mattias Nissler (ping if slow), 2011/03/16 17:40:00]

Done.

+    CONFIG_UNSET
+  };
+
   // Observer for being notified when the proxy settings have changed.
   class Observer {
    public:
     virtual ~Observer() {}
-    virtual void OnProxyConfigChanged(const ProxyConfig& config) = 0;
+    virtual void OnProxyConfigChanged(const ProxyConfig& config,

[eroman, 2011/03/16 01:30:00]

Could you add a comment explaining that |availability| will NEVER be
CONFIG_PENDING here.

And moreover, that |config| is only interesting when availability ==
CONFIG_VALID.

[Mattias Nissler (ping if slow), 2011/03/16 17:40:00]

Done.

+                                      ConfigAvailability availability) = 0;
   };
 
   virtual ~ProxyConfigService() {}
@@ -33,7 +44,7 @@ class ProxyConfigService {
   // some point in the future once the configuration is available.
   // Note that to avoid re-entrancy problems, implementations should not
   // dispatch any change notifications from within this function.
-  virtual bool GetLatestProxyConfig(ProxyConfig* config) = 0;
+  virtual ConfigAvailability GetLatestProxyConfig(ProxyConfig* config) = 0;
 
   // ProxyService will call this periodically during periods of activity.
   // It can be used as a signal for polling-based implementations.