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

ui/app_list/views/app_list_main_view.cc

 // Copyright 2013 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/app_list_main_view.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
 #include "ui/app_list/app_list_constants.h"
 #include "ui/app_list/app_list_folder_item.h"
 #include "ui/app_list/app_list_item.h"
 #include "ui/app_list/app_list_model.h"
 #include "ui/app_list/app_list_switches.h"
 #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"
 #include "ui/app_list/views/contents_switcher_view.h"
 #include "ui/app_list/views/contents_view.h"
 #include "ui/app_list/views/search_box_view.h"
 #include "ui/views/controls/textfield/textfield.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/fill_layout.h"
 #include "ui/views/widget/widget.h"
@@ skipping 263 matching lines @@
   else
     item->Activate(event_flags);
 }
 
 void AppListMainView::GetShortcutPathForApp(
     const std::string& app_id,
     const base::Callback<void(const base::FilePath&)>& callback) {
   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);
   bool should_show_search = !query.empty();
   contents_view_->ShowSearchResults(should_show_search);
   UpdateSearchBoxVisibility();
 
   if (should_show_search)
     delegate_->StartSearch();
   else
@@ skipping 10 matching lines @@
   // Resubmit the query via a posted task so that all observers for the
   // uninstall notification are notified.
   base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(&AppListMainView::QueryChanged,
                  weak_ptr_factory_.GetWeakPtr(),
                  search_box_view_));
 }
 
 }  // namespace app_list