aura: Remove event-dispatch methods from WindowTreeHostDelegate interface.

ash/drag_drop/drag_drop_controller_unittest.cc

Index: ash/drag_drop/drag_drop_controller_unittest.cc
diff --git a/ash/drag_drop/drag_drop_controller_unittest.cc b/ash/drag_drop/drag_drop_controller_unittest.cc
index 8ad42712b9f0a7ff4726ae4212d216e33cbc2864..241edb26217fd8a7172763c1e0c717200fe63962 100644
--- a/ash/drag_drop/drag_drop_controller_unittest.cc
+++ b/ash/drag_drop/drag_drop_controller_unittest.cc
@@ -737,8 +737,9 @@ TEST_F(DragDropControllerTest, SyntheticEventsDuringDragDrop) {
     gfx::Point mouse_move_location = drag_view->bounds().CenterPoint();
     ui::MouseEvent mouse_move(ui::ET_MOUSE_MOVED, mouse_move_location,
                               mouse_move_location, 0, 0);
-    Shell::GetPrimaryRootWindow()->GetDispatcher()->AsWindowTreeHostDelegate()->
-        OnHostMouseEvent(&mouse_move);
+    ui::EventDispatchDetails details = Shell::GetPrimaryRootWindow()->
+        GetDispatcher()->OnEventFromSource(&mouse_move);
+    ASSERT_FALSE(details.dispatcher_destroyed);
   }
 
   generator.ReleaseLeftButton();