Add a unit test for resetting the app list on a reshow.

ui/app_list/views/apps_container_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/apps_container_view.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 25 matching lines @@
     rows = kExperimentalPreferredRows;
   }
   apps_grid_view_->SetLayout(kPreferredIconDimension, cols, rows);
   AddChildView(apps_grid_view_);
 
   folder_background_view_ = new FolderBackgroundView();
   AddChildView(folder_background_view_);
 
   app_list_folder_view_ =
       new AppListFolderView(this, model, app_list_main_view);
+  // The folder view is initially hidden.
+  app_list_folder_view_->SetVisible(false);
   AddChildView(app_list_folder_view_);
 
   apps_grid_view_->SetModel(model_);
   apps_grid_view_->SetItemList(model_->top_level_item_list());
   SetShowState(SHOW_APPS,
                false);  /* show apps without animation */
 }
 
 AppsContainerView::~AppsContainerView() {
 }
@@ skipping 145 matching lines @@
 
 void AppsContainerView::CreateViewsForFolderTopItemsAnimation(
     AppListFolderItem* active_folder,
     bool open_folder) {
   top_icon_views_.clear();
   std::vector<gfx::Rect> top_items_bounds =
       GetTopItemIconBoundsInActiveFolder();
   top_icon_animation_pending_count_ =
       std::min(kNumFolderTopItems, active_folder->item_list()->item_count());
   for (size_t i = 0; i < top_icon_animation_pending_count_; ++i) {
+    if (active_folder->GetTopIcon(i).isNull())
+      continue;
+
     TopIconAnimationView* icon_view = new TopIconAnimationView(
         active_folder->GetTopIcon(i), top_items_bounds[i], open_folder);
     icon_view->AddObserver(this);
     top_icon_views_.push_back(icon_view);
 
     // Add the transitional views into child views, and set its bounds to the
     // same location of the item in the folder list view.
     AddChildView(top_icon_views_[i]);
     top_icon_views_[i]->SetBoundsRect(
         app_list_folder_view_->ConvertRectToParent(
             app_list_folder_view_->GetItemIconBoundsAt(i)));
     static_cast<TopIconAnimationView*>(top_icon_views_[i])->TransformView();
   }
 }
 
 void AppsContainerView::PrepareToShowApps(AppListFolderItem* folder_item) {
   if (folder_item)
     CreateViewsForFolderTopItemsAnimation(folder_item, false);
 
   // Hide the active folder item until the animation completes.
   if (apps_grid_view_->activated_item_view())
     apps_grid_view_->activated_item_view()->SetVisible(false);
 }
 
 }  // namespace app_list