Convert Aura to use ui::Event.

ui/aura/test/event_generator.h

Index: ui/aura/test/event_generator.h
===================================================================
--- ui/aura/test/event_generator.h	(revision 150582)
+++ ui/aura/test/event_generator.h	(working copy)
@@ -13,8 +13,11 @@
 class TimeDelta;
 }
 
+namespace ui {
+class Event;
+}
+
 namespace aura {
-class Event;
 class RootWindow;
 class Window;
 
@@ -165,7 +168,7 @@
   void ReleaseKey(ui::KeyboardCode key_code, int flags);
 
   // Dispatch the |event| to the RootWindow.
-  void Dispatch(Event& event);
+  void Dispatch(ui::Event& event);
 
  private:
   // Dispatch a key event to the RootWindow.