Notify launcher page with onTransitionChanged event

ui/app_list/views/contents_switcher_view.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/app_list/views/contents_switcher_view.h"
 
 #include "ui/app_list/views/contents_view.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/controls/button/image_button.h"
@@ skipping 43 matching lines @@
 void ContentsSwitcherView::SelectedPageChanged(int old_selected,
                                                int new_selected) {
   // TODO(mgiuca): Visually indicate which page is now selected.
 }
 
 void ContentsSwitcherView::TransitionStarted() {
 }
 
 void ContentsSwitcherView::TransitionChanged() {
   // Change the indicator during a launcher page transition.
-  const PaginationModel& pm = contents_view_->pagination_model();
-  int old_selected = pm.selected_page();
-  int new_selected = pm.transition().target_page;
-  if (pm.IsRevertingCurrentTransition()) {
+  const PaginationModel* pm = contents_view_->pagination_model();
+  int old_selected = pm->selected_page();
+  int new_selected = pm->transition().target_page;
+  if (pm->IsRevertingCurrentTransition()) {
     // Swap the direction if the transition is reversed.
-    old_selected = pm.transition().target_page;
-    new_selected = pm.selected_page();
+    old_selected = pm->transition().target_page;
+    new_selected = pm->selected_page();
   }
 
   SelectedPageChanged(old_selected, new_selected);
 }
 
 }  // namespace app_list