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

chrome/browser/content_settings/content_settings_policy_provider.h

Index: chrome/browser/content_settings/content_settings_policy_provider.h
diff --git a/chrome/browser/content_settings/content_settings_policy_provider.h b/chrome/browser/content_settings/content_settings_policy_provider.h
index f634da77f4d2af13437bf4ccebd87f129152caeb..2b34cfb4afe8595b1c78122ecb2126a3423d9b6d 100644
--- a/chrome/browser/content_settings/content_settings_policy_provider.h
+++ b/chrome/browser/content_settings/content_settings_policy_provider.h
@@ -14,7 +14,7 @@
 #include "base/synchronization/lock.h"
 #include "base/tuple.h"
 #include "chrome/browser/content_settings/content_settings_origin_identifier_value_map.h"
-#include "chrome/browser/content_settings/content_settings_provider.h"
+#include "chrome/browser/content_settings/content_settings_abstract_provider.h"
 #include "chrome/browser/prefs/pref_change_registrar.h"
 #include "content/common/notification_observer.h"
 #include "content/common/notification_registrar.h"
@@ -78,16 +78,16 @@ class PolicyDefaultProvider : public DefaultProviderInterface,
 };
 
 // PolicyProvider that provider managed content-settings.
-class PolicyProvider : public ProviderInterface,
+class PolicyProvider : public AbstractProvider,
                        public NotificationObserver {
  public:
-  PolicyProvider(HostContentSettingsMap* map,
+  PolicyProvider(Observer* observer,

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

Come to think of it, do we actually *need* an observer in the constructor? If an
ObservableProvider has an arbitrary number of observers (as opposed to exactly
one), it should also be possible to have zero (like for the unit test case).

[markusheintz_, 2011/07/13 13:28:53]

That is totally correct!

Basically the host content settings map need to call AddObserver(this) after
creating a content setting provider and RemoveObserver(this) when it is 
shutdown.

I implemented this originally and I'm very in favor of that solution.

I will also have to change the ProviderPtr type in the HostContentSettingsMap to
point the an ObservableProvider (AbstractProvider)

[Bernhard Bauer, 2011/07/13 13:41:32]

No, you don't. At the point where you create the concrete Provider, you know its
exact type, so you can call ObservableProvider methods on it, but the elements
of the provider list only need to be of type Provider.

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

Ok.

                  PrefService* prefs,
                  DefaultProviderInterface* default_provider);
   virtual ~PolicyProvider();
   static void RegisterUserPrefs(PrefService* prefs);
 
-  // ProviderInterface Implementation
+  // ProviderInterface implementations.
   virtual void SetContentSetting(
       const ContentSettingsPattern& primary_pattern,
       const ContentSettingsPattern& secondary_pattern,
@@ -131,11 +131,8 @@ class PolicyProvider : public ProviderInterface,
 
   void ReadManagedContentSettingsTypes(ContentSettingsType content_type);
 
-  void NotifyObservers(const ContentSettingsDetails& details);
-
   OriginIdentifierValueMap value_map_;
 
-  HostContentSettingsMap* host_content_settings_map_;
   PrefService* prefs_;
 
   // Weak, owned by HostContentSettingsMap.