Add callback list to PrefModelAssociator after sync data is loaded

components/content_settings/core/browser/host_content_settings_map.h

 // Copyright (c) 2012 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.
 
 // Maps hostnames to custom content settings.  Written on the UI thread and read
 // on any thread.  One instance per profile.
 
 #ifndef COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_HOST_CONTENT_SETTINGS_MAP_H_
 #define COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_HOST_CONTENT_SETTINGS_MAP_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_checker.h"
 #include "components/content_settings/core/browser/content_settings_observer.h"
 #include "components/content_settings/core/browser/content_settings_utils.h"
 #include "components/content_settings/core/common/content_settings.h"
 #include "components/content_settings/core/common/content_settings_pattern.h"
 #include "components/content_settings/core/common/content_settings_types.h"
 #include "components/keyed_service/core/refcounted_keyed_service.h"
 #include "components/prefs/pref_change_registrar.h"
+#include "components/syncable_prefs/pref_service_syncable.h"
 
 class ExtensionService;
 class GURL;
 class PrefService;
 
 namespace base {
 class Clock;
 class Value;
 }
 
 namespace content_settings {
 class ObservableProvider;
 class ProviderInterface;
 class PrefProvider;
 class TestUtils;
 }
 
+namespace syncable_prefs {
+class PrefServiceSyncable;
+}
+
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 class HostContentSettingsMap : public content_settings::Observer,
                                public RefcountedKeyedService {
  public:
   enum ProviderType {
     // EXTENSION names is a layering violation when this class will move to
     // components.
     // TODO(mukai): find the solution.
     INTERNAL_EXTENSION_PROVIDER = 0,
     POLICY_PROVIDER,
     SUPERVISED_PROVIDER,
     CUSTOM_EXTENSION_PROVIDER,
     PREF_PROVIDER,
     DEFAULT_PROVIDER,
     NUM_PROVIDER_TYPES
   };
 
   // This should be called on the UI thread, otherwise |thread_checker_| handles
   // CalledOnValidThread() wrongly. Only one (or neither) of
   // |is_incognito_profile| and |is_guest_profile| should be true.
   HostContentSettingsMap(PrefService* prefs,
                          bool is_incognito_profile,
-                         bool is_guest_profile);
+                         bool is_guest_profile,
+                         syncable_prefs::PrefServiceSyncable* pref_service);

[raymes, 2016/06/29 03:50:01]

I'm wondering if we can just pass in a base::Callback here
register_pref_sync_finished_callback

register_pref_sync_finished_callback.Run(base::Bind(...));

That would eliminate the dependency on syncable_prefs and make testing a lot
easier.

We could even register the callback outside this class (without passing anything
in), but I think this is slightly better because it means that the client code
is forced to think about registering such a callback. What do you think?

[lshang, 2016/06/30 05:03:36]

Done. 
Yeah as we discussed, I think register the callback outside this class sounds
better because that will make the constructor of HostContentSettingsMap cleaner.
I've moved it to HostContentSettingsMapFactory. And I also commented out the
registration code block for now since we don't really want it to be called in
this CL. we should hook all things up in the next CL when we change the scoping
type.

 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
   // Adds a new provider for |type|.
   void RegisterProvider(
       ProviderType type,
       std::unique_ptr<content_settings::ObservableProvider> provider);
 
   // Returns the default setting for a particular content type. If |provider_id|
   // is not NULL, the id of the provider which provided the default setting is
@@ skipping 309 matching lines @@
   // before any other uses of it.
   ProviderMap content_settings_providers_;
 
   // content_settings_providers_[PREF_PROVIDER] but specialized.
   content_settings::PrefProvider* pref_provider_ = nullptr;
 
   base::ThreadChecker thread_checker_;
 
   base::ObserverList<content_settings::Observer> observers_;
 
+  syncable_prefs::PrefServiceSyncable* pref_service_;
+
   DISALLOW_COPY_AND_ASSIGN(HostContentSettingsMap);
 };
 
 #endif  // COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_HOST_CONTENT_SETTINGS_MAP_H_