[Sync] Make generic non-frontend thread datatype controller.

chrome/browser/sync/glue/frontend_data_type_controller.h

Index: chrome/browser/sync/glue/frontend_data_type_controller.h
diff --git a/chrome/browser/sync/glue/frontend_data_type_controller.h b/chrome/browser/sync/glue/frontend_data_type_controller.h
index d228bb99a6297845e58bf12e0965baa2245f45f4..6a2d86313abf9ce7c5d08a33558676eeefe43b74 100644
--- a/chrome/browser/sync/glue/frontend_data_type_controller.h
+++ b/chrome/browser/sync/glue/frontend_data_type_controller.h
@@ -22,6 +22,8 @@ namespace browser_sync {
 class AssociatorInterface;
 class ChangeProcessor;
 
+// TODO(zea): have naming and style match NonFrontendDataTypeController.
+// TODO(zea): Rename frontend to UI (http://crbug.com/78833).
 // Implementation for datatypes that reside on the frontend thread
 // (UI thread). This is the same thread we perform initialization on, so we
 // don't have to worry about thread safety. The main start/stop funtionality is
@@ -44,15 +46,10 @@ class FrontendDataTypeController : public DataTypeController {
 
   // DataTypeController interface.
   virtual void Start(StartCallback* start_callback);
-
   virtual void Stop();
-
   virtual syncable::ModelType type() const = 0;
-
   virtual browser_sync::ModelSafeGroup model_safe_group() const;
-
   virtual std::string name() const;
-
   virtual State state() const;
 
   // UnrecoverableErrorHandler interface.
@@ -64,25 +61,33 @@ class FrontendDataTypeController : public DataTypeController {
 
   // Kick off any dependent services that need to be running before we can
   // associate models. The default implementation is a no-op.
+  // Return value:
+  //   True - if models are ready and association can proceed.
+  //   False - if models are not ready. Associate() should be called when the
+  //           models are ready. Refer to Start(_) implementation.
   virtual bool StartModels();
 
   // Build sync components and associate models.
+  // Return value:
+  //   True - if association was successful. FinishStart should have been
+  //          invoked.
+  //   False - if association failed. StartFailed should have been invoked.
   virtual bool Associate();
 
+  // Datatype specific creation of sync components.
+  virtual void CreateSyncComponents() = 0;
+
   // Perform any DataType controller specific state cleanup before stopping
   // the datatype controller. The default implementation is a no-op.
-  virtual void CleanupState();
-
-  // Helper method to run the stashed start callback with a given result.
-  virtual void FinishStart(StartResult result,
-      const tracked_objects::Location& from_here);
+  virtual void CleanUpState();
 
   // Cleans up state and calls callback when start fails.
   virtual void StartFailed(StartResult result,
       const tracked_objects::Location& from_here);
 
-  // Datatype specific creation of sync components.
-  virtual void CreateSyncComponents() = 0;
+  // Helper method to run the stashed start callback with a given result.
+  virtual void FinishStart(StartResult result,
+      const tracked_objects::Location& from_here);
 
   // DataType specific histogram methods. Because histograms use static's, the
   // specific datatype controllers must implement this themselves.