[sync] Refactor how default sync datatypes are set.

chrome/browser/sync/profile_sync_components_factory_impl.h

Index: chrome/browser/sync/profile_sync_components_factory_impl.h
diff --git a/chrome/browser/sync/profile_sync_components_factory_impl.h b/chrome/browser/sync/profile_sync_components_factory_impl.h
index 241cc8f711c458900c290cae7e1e24b9e17a92d4..862b3c22b02ad1a6e2b8fd2039763ee199dac67f 100644
--- a/chrome/browser/sync/profile_sync_components_factory_impl.h
+++ b/chrome/browser/sync/profile_sync_components_factory_impl.h
@@ -64,6 +64,11 @@ class ProfileSyncComponentsFactoryImpl : public ProfileSyncComponentsFactory {
       browser_sync::DataTypeErrorHandler* error_handler) OVERRIDE;
 
  private:
+  // Register data types which are enabled on desktop platforms only.
+  void RegisterDesktopDataTypes(ProfileSyncService* pss);
+  // Register data types which are enabled on both desktop and mobile.
+  void RegisterCommonDataTypes(ProfileSyncService* pss);
+
   Profile* profile_;
   CommandLine* command_line_;
   // Set on the UI thread (since extensions::ExtensionSystemFactory is