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

chrome/browser/content_settings/content_settings_abstract_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_ABSTRACT_PROVIDER_H_
+#define CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_ABSTRACT_PROVIDER_H_
+
+#include <set>
+
+#include "chrome/browser/content_settings/content_settings_details.h"
+#include "chrome/browser/content_settings/content_settings_provider.h"
+#include "chrome/browser/content_settings/content_settings_observer.h"
+
+namespace content_settings {
+
+class AbstractProvider : public ProviderInterface {

[Bernhard Bauer, 2011/07/13 07:58:18]

Seeing as this class mainly manages Observers, maybe you could call it
ObservingProvider?

[markusheintz_, 2011/07/13 12:48:16]

How about ObservableProvider as the provider can be observed but it does not
observe anything.

[Bernhard Bauer, 2011/07/13 13:21:28]

Sounds good.

[markusheintz_, 2011/07/13 14:14:42]

Done.

+ public:
+  typedef std::set<Observer*> ObserverSet;
+
+  AbstractProvider();
+  virtual ~AbstractProvider();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // ProviderInterface implementation

[Bernhard Bauer, 2011/07/13 07:58:18]

Do you need to declare these methods again?

[markusheintz_, 2011/07/13 12:48:16]

No I just though it might be helpful for people to notice that this class has
pure virtual methods.

I'm totally ok with removing them.

+  virtual ContentSetting GetContentSetting(
+      const GURL& primary_url,
+      const GURL& secondary_url,
+      ContentSettingsType content_type,
+      const ResourceIdentifier& resource_identifier) const = 0;
+
+  virtual void SetContentSetting(
+      const ContentSettingsPattern& primary_pattern,
+      const ContentSettingsPattern& secondary_pattern,
+      ContentSettingsType content_type,
+      const ResourceIdentifier& resource_identifier,
+      ContentSetting content_setting) = 0;
+
+  virtual void GetAllContentSettingsRules(
+      ContentSettingsType content_type,
+      const ResourceIdentifier& resource_identifier,
+      Rules* content_setting_rules) const = 0;
+
+  virtual void ClearAllContentSettingsRules(
+      ContentSettingsType content_type) = 0;
+
+  virtual void ShutdownOnUIThread() = 0;
+
+ protected:
+  void NotifyObservers(const ContentSettingsDetails& details) const;
+  void RemoveAllObserver();

[Bernhard Bauer, 2011/07/13 07:58:18]

This method name should read |RemoveAllObservers| (plural).

[markusheintz_, 2011/07/13 12:48:16]

Done.

+
+ private:
+  ObserverSet observers_;
+};
+
+}  // namespace content_settings
+
+#endif  // CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_ABSTRACT_PROVIDER_H_