Notify launcher page with onTransitionChanged event

ui/app_list/views/contents_switcher_view.cc

Index: ui/app_list/views/contents_switcher_view.cc
diff --git a/ui/app_list/views/contents_switcher_view.cc b/ui/app_list/views/contents_switcher_view.cc
index 29d500834baa79d8eb0d49fbc66177ed3e377b63..24932386e1192416276ed4fded7a0cae18640449 100644
--- a/ui/app_list/views/contents_switcher_view.cc
+++ b/ui/app_list/views/contents_switcher_view.cc
@@ -61,13 +61,13 @@ 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);