[Sync] Convert DTCs to be not RefCounted and NonThreadSafe.

components/history/core/browser/history_delete_directives_data_type_controller.h

Index: components/history/core/browser/history_delete_directives_data_type_controller.h
diff --git a/components/history/core/browser/history_delete_directives_data_type_controller.h b/components/history/core/browser/history_delete_directives_data_type_controller.h
index e76115e0e07380f24d16b96ddc14cfa753d93dc1..5af4b82a47be272db18712a6057951cb7a869ccd 100644
--- a/components/history/core/browser/history_delete_directives_data_type_controller.h
+++ b/components/history/core/browser/history_delete_directives_data_type_controller.h
@@ -19,9 +19,9 @@ class HistoryDeleteDirectivesDataTypeController
       public sync_driver::SyncServiceObserver {
  public:
   HistoryDeleteDirectivesDataTypeController(
-      const scoped_refptr<base::SingleThreadTaskRunner>& ui_thread,
-      const base::Closure& error_callback,
+      const base::Closure& dump_stack,

[sky, 2016/09/02 14:06:28]

I have to say that it isn't at all clear what dump_stack means in any of these
classes. It would be nice there was a description so I don't have to go for the
base class to understand what it is.

[maxbogue, 2016/09/02 21:15:08]

I've added a comment above all the DTC constructors that tries to clarify it a
little bit. Hopefully in the future we can remove that parameter entirely.

       sync_driver::SyncClient* sync_client);
+  ~HistoryDeleteDirectivesDataTypeController() override;
 
   // UIDataTypeController override.
   bool ReadyForStart() const override;
@@ -32,9 +32,6 @@ class HistoryDeleteDirectivesDataTypeController
   void OnStateChanged() override;
 
  private:
-  // Refcounted.
-  ~HistoryDeleteDirectivesDataTypeController() override;
-
   // Triggers a SingleDataTypeUnrecoverable error and returns true if the
   // type is no longer ready, else does nothing and returns false.
   bool DisableTypeIfNecessary();