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

chrome/browser/content_settings/content_settings_abstract_provider.cc

+// 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.
+
+#include "chrome/browser/content_settings/content_settings_abstract_provider.h"
+
+namespace content_settings {
+
+AbstractProvider::AbstractProvider() {
+}
+
+AbstractProvider::~AbstractProvider() {
+  DCHECK(observer_list_.size() == 0);
+}
+
+void AbstractProvider::AddObserver(Observer* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void AbstractProvider::RemoveObserver(Observer* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
+void AbstractProvider::RemoveAllObservers() {
+  observer_list_.Clear();
+}
+
+void AbstractProvider::NotifyObservers(
+    ContentSettingsPattern primary_pattern,
+    ContentSettingsPattern secondary_pattern,
+    ContentSettingsType content_type,
+    std::string resource_identifier) {
+  FOR_EACH_OBSERVER(Observer,
+                    observer_list_,
+                    OnContentSettingChanged(
+                        primary_pattern,
+                        secondary_pattern,
+                        content_type,
+                        resource_identifier));
+}
+
+}  // namespace content_settings