Make the hcsm and its providers communicate via an observer interface.

chrome/browser/content_settings/content_settings_observable_provider.h

+// 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.
+
+#ifndef CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OBSERVABLE_PROVIDER_H_
+#define CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OBSERVABLE_PROVIDER_H_
+
+#include <set>
+#include <string>
+
+#include "base/observer_list.h"
+#include "chrome/browser/content_settings/content_settings_provider.h"
+#include "chrome/browser/content_settings/content_settings_observer.h"
+
+namespace content_settings {
+
+class ObservableProvider : public ProviderInterface {
+ public:
+  ObservableProvider();
+  virtual ~ObservableProvider();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+ protected:
+  void NotifyObservers(ContentSettingsPattern primary_pattern,
+                       ContentSettingsPattern secondary_pattern,
+                       ContentSettingsType content_type,
+                       std::string resource_identifier);
+  void RemoveAllObservers();
+
+ private:
+  ObserverList<Observer, true> observer_list_;
+};
+
+}  // namespace content_settings
+
+#endif  // CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OBSERVABLE_PROVIDER_H_