Makes DesktopWindowTreeHostXxx to dispatch key event to InputMethod.

ui/events/event_source.h

Index: ui/events/event_source.h
diff --git a/ui/events/event_source.h b/ui/events/event_source.h
index f545eea82f417ff3eb9f1802e3a06ed2fc556b82..d369c3402d86061b7b508d100c56990075af3303 100644
--- a/ui/events/event_source.h
+++ b/ui/events/event_source.h
@@ -34,11 +34,12 @@ class EVENTS_EXPORT EventSource {
 
  protected:
   EventDispatchDetails SendEventToProcessor(Event* event);
-  virtual EventDispatchDetails DeliverEventToProcessor(Event* event);
 
  private:
   friend class EventSourceTestApi;
 
+  EventDispatchDetails DeliverEventToProcessor(Event* event);
+
   typedef std::vector<EventRewriter*> EventRewriterList;
   EventRewriterList rewriter_list_;
   DISALLOW_COPY_AND_ASSIGN(EventSource);