Fix app list DCHECKs getting hit when model updates occur during dragging

ui/app_list/views/app_list_main_view.cc

Index: ui/app_list/views/app_list_main_view.cc
diff --git a/ui/app_list/views/app_list_main_view.cc b/ui/app_list/views/app_list_main_view.cc
index 2cbe4f68e5dcb1fac2db1755fb991b5d794b2f57..c0f7a832cb19717779ca47346a3ee56c3d3ad281 100644
--- a/ui/app_list/views/app_list_main_view.cc
+++ b/ui/app_list/views/app_list_main_view.cc
@@ -19,6 +19,7 @@
 #include "ui/app_list/app_list_view_delegate.h"
 #include "ui/app_list/pagination_model.h"
 #include "ui/app_list/search_box_model.h"
+#include "ui/app_list/views/app_list_folder_view.h"
 #include "ui/app_list/views/app_list_item_view.h"
 #include "ui/app_list/views/apps_container_view.h"
 #include "ui/app_list/views/apps_grid_view.h"
@@ -302,6 +303,13 @@ void AppListMainView::GetShortcutPathForApp(
   delegate_->GetShortcutPathForApp(app_id, callback);
 }
 
+void AppListMainView::CancelDragInActiveFolder() {
+  contents_view_->apps_container_view()
+      ->app_list_folder_view()
+      ->items_grid_view()
+      ->EndDrag(true);
+}
+
 void AppListMainView::QueryChanged(SearchBoxView* sender) {
   base::string16 query;
   base::TrimWhitespace(model_->search_box()->text(), base::TRIM_ALL, &query);