Add callback list to PrefModelAssociator after sync data is loaded

components/content_settings/core/browser/host_content_settings_map.h

Index: components/content_settings/core/browser/host_content_settings_map.h
diff --git a/components/content_settings/core/browser/host_content_settings_map.h b/components/content_settings/core/browser/host_content_settings_map.h
index 9115c2836a932b70c52fada8c8d6c27a991f454e..1113f6256773afe972b2871f3c7354d300281ab6 100644
--- a/components/content_settings/core/browser/host_content_settings_map.h
+++ b/components/content_settings/core/browser/host_content_settings_map.h
@@ -278,6 +278,14 @@ class HostContentSettingsMap : public content_settings::Observer,
   // Passes ownership of |clock|.
   void SetPrefClockForTesting(std::unique_ptr<base::Clock> clock);
 
+  // Migrate old domain scoped ALLOW settings to be origin scoped for
+  // ContentSettingsTypes which are domain scoped. Only narrow down ALLOW
+  // domain settings to origins so that this will not cause privacy/security
+  // issues.
+  // TODO(lshang): https://crbug.com/621398 Remove this when clients have
+  // migrated (~M55).
+  void MigrateDomainScopedSettings();
+
  private:
   friend class base::RefCountedThreadSafe<HostContentSettingsMap>;
   friend class HostContentSettingsMapTest_MigrateDomainScopedSettings_Test;
@@ -312,14 +320,6 @@ class HostContentSettingsMap : public content_settings::Observer,
   // leave in some code to remove old-format settings for a long time.
   void MigrateKeygenSettings();
 
-  // Migrate old domain scoped ALLOW settings to be origin scoped for
-  // ContentSettingsTypes which are domain scoped. Only narrow down ALLOW
-  // domain settings to origins so that this will not cause privacy/security
-  // issues.
-  // TODO(lshang): https://crbug.com/621398 Remove this when clients have
-  // migrated (~M56).
-  void MigrateDomainScopedSettings();
-
   // Collect UMA data about the number of exceptions.
   void RecordNumberOfExceptions();