Change the ProxyConfigService interface to be asynchronous, and support observers.

The Windows implementation is still using a polling mechanism under the hood, however that polling has been moved to the worker pool so it won't block the IO thread in case WinHttpGetIEProxyConfigForCurrentUser is slow (crbug.com/12189).

BUG=12189

Review URL: http://codereview.chromium.org/3056011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53442 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 30 insertions, 7 deletions

diff --git a/net/proxy/proxy_config_service.h b/net/proxy/proxy_config_service.h
index 9f6bb50..1c65e3a 100644
--- a/net/proxy/proxy_config_service.h
+++ b/net/proxy/proxy_config_service.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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.
 
@@ -9,16 +9,39 @@ namespace net {
 
 class ProxyConfig;
 
-// Synchronously fetch the system's proxy configuration settings. Called on
-// the IO Thread.
+// Service for watching when the proxy settings have changed.
 class ProxyConfigService {
  public:
+  // Observer for being notified when the proxy settings have changed.
+  class Observer {
+   public:
+    virtual ~Observer() {}
+    virtual void OnProxyConfigChanged(const ProxyConfig& config) = 0;
+  };
+
   virtual ~ProxyConfigService() {}
 
-  // Get the proxy configuration.  Returns OK if successful or an error code if
-  // otherwise.  |config| should be in its initial state when this method is
-  // called.
-  virtual int GetProxyConfig(ProxyConfig* config) = 0;
+  // Adds/Removes an observer that will be called whenever the proxy
+  // configuration has changed.
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+
+  // Gets the most recent value of the proxy configuration. Returns false if
+  // it is not available yet. In the case where we returned false, it is
+  // guaranteed that subscribed observers will be notified of a change at
+  // 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;
+
+  // ProxyService will call this periodically during periods of activity.
+  // It can be used as a signal for polling-based implementations.
+  //
+  // Note that this is purely used as an optimization -- polling
+  // implementations could simply set a global timer that goes off every
+  // X seconds at which point they check for changes. However that has
+  // the disadvantage of doing continuous work even during idle periods.
+  virtual void OnLazyPoll() {}
 };
 
 }  // namespace net