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

ui/app_list/views/apps_grid_view_unittest.cc

 // Copyright (c) 2012 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/apps_grid_view.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
@@ skipping 289 matching lines @@
   // Deleting an item keeps remaining intact.
   SimulateDrag(AppsGridView::MOUSE, from, to);
   model_->DeleteItem(model_->GetItemName(0));
   apps_grid_view_->EndDrag(false);
   EXPECT_EQ(std::string("Item 1,Item 2,Item 3"),
             model_->GetModelContent());
   test_api_->LayoutToIdealBounds();
 
   // Adding a launcher item cancels the drag and respects the order.
   SimulateDrag(AppsGridView::MOUSE, from, to);
+  EXPECT_TRUE(apps_grid_view_->has_dragged_view());
   model_->CreateAndAddItem("Extra");
-  apps_grid_view_->EndDrag(false);
+  // No need to EndDrag explicitly - adding an item should do this.
+  EXPECT_FALSE(apps_grid_view_->has_dragged_view());
+  // Even though cancelled, mouse move events can still arrive via the item
+  // view. Ensure that behaves sanely, and doesn't start a new drag.
+  ui::MouseEvent drag_event(
+      ui::ET_MOUSE_DRAGGED, gfx::Point(1, 1), gfx::Point(2, 2), 0, 0);
+  apps_grid_view_->UpdateDragFromItem(AppsGridView::MOUSE, drag_event);
+  EXPECT_FALSE(apps_grid_view_->has_dragged_view());
+
   EXPECT_EQ(std::string("Item 1,Item 2,Item 3,Extra"),
             model_->GetModelContent());
   test_api_->LayoutToIdealBounds();
 }
 
 TEST_F(AppsGridViewTest, MouseDragItemIntoFolder) {
   EnsureFoldersEnabled();
 
   size_t kTotalItems = 3;
   model_->PopulateApps(kTotalItems);
@@ skipping 379 matching lines @@
   AppListItemView* item_view = GetItemViewAt(0);
   ASSERT_TRUE(item_view);
   const views::Label* title_label = item_view->title();
   EXPECT_FALSE(title_label->GetTooltipText(
       title_label->bounds().CenterPoint(), &actual_tooltip));
   EXPECT_EQ(title, base::UTF16ToUTF8(title_label->text()));
 }
 
 }  // namespace test
 }  // namespace app_list