Change ContentSettingsType's scoping type and hookup migration code

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 6b0f04e88176a1c09b5d8c131648ce25256979f1..e35d84da0b615810e2eddc9254d39eac6e1790fe 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 +278,16 @@ 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 (~M56).
+  void MigrateDomainScopedSettings(bool after_sync);
+
+  base::WeakPtr<HostContentSettingsMap> GetWeakPtr();
+
  private:
   friend class base::RefCountedThreadSafe<HostContentSettingsMap>;
   friend class HostContentSettingsMapTest_DomainToOriginMigrationStatus_Test;
@@ -313,14 +323,6 @@ 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(bool after_sync);
-
   // Collect UMA data about the number of exceptions.
   void RecordNumberOfExceptions();
 
@@ -397,6 +399,8 @@ class HostContentSettingsMap : public content_settings::Observer,
 
   base::ObserverList<content_settings::Observer> observers_;
 
+  base::WeakPtrFactory<HostContentSettingsMap> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(HostContentSettingsMap);
 };