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

chrome/browser/content_settings/content_settings_extension_provider.cc

Index: chrome/browser/content_settings/content_settings_extension_provider.cc
diff --git a/chrome/browser/content_settings/content_settings_extension_provider.cc b/chrome/browser/content_settings/content_settings_extension_provider.cc
index 9dcf9ae98dcb09d5230b39dd023bd6c2ebe02c4e..b350ec4620f905b0a8715f6317169a371b4fea35 100644
--- a/chrome/browser/content_settings/content_settings_extension_provider.cc
+++ b/chrome/browser/content_settings/content_settings_extension_provider.cc
@@ -15,17 +15,16 @@
 namespace content_settings {
 
 ExtensionProvider::ExtensionProvider(
-    HostContentSettingsMap* map,
+    content_settings::Observer* observer,
     ExtensionContentSettingsStore* extensions_settings,
     bool incognito)
-    : map_(map),
-      incognito_(incognito),
+    : incognito_(incognito),
       extensions_settings_(extensions_settings) {
+  AddObserver(observer);
   extensions_settings_->AddObserver(this);
 }
 
 ExtensionProvider::~ExtensionProvider() {
-  DCHECK(!map_);
 }
 
 ContentSetting ExtensionProvider::GetContentSetting(
@@ -53,17 +52,8 @@ void ExtensionProvider::GetAllContentSettingsRules(
 }
 
 void ExtensionProvider::ShutdownOnUIThread() {
+  RemoveAllObserver();
   extensions_settings_->RemoveObserver(this);
-  map_ = NULL;
-}
-
-void ExtensionProvider::NotifyObservers(
-    const ContentSettingsDetails& details) {
-  DCHECK(map_);
-  NotificationService::current()->Notify(
-      chrome::NOTIFICATION_CONTENT_SETTINGS_CHANGED,
-      Source<HostContentSettingsMap>(map_),
-      Details<const ContentSettingsDetails>(&details));
 }
 
 void ExtensionProvider::OnContentSettingChanged(