app_list: Fix SearchResultView result_ usage.

ui/app_list/views/search_result_view.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/search_result_view.h"
 
 #include <algorithm>
 
 #include "ui/app_list/app_list_constants.h"
 #include "ui/app_list/search_result.h"
@@ skipping 154 matching lines @@
   const int progress_height = progress_bar_->GetPreferredSize().height();
   const gfx::Rect progress_bounds(
       rect.right() - kActionButtonRightMargin - progress_width,
       rect.y() + (rect.height() - progress_height) / 2,
       progress_width,
       progress_height);
   progress_bar_->SetBoundsRect(progress_bounds);
 }
 
 bool SearchResultView::OnKeyPressed(const ui::KeyEvent& event) {
-  DCHECK(result_);
+  // |result_| could be NULL when result list is changing.
+  if (!result_)
+    return false;
 
   switch (event.key_code()) {
     case ui::VKEY_TAB: {
       int new_selected = actions_view_->selected_action()
           + (event.IsShiftDown() ? -1 : 1);
       actions_view_->SetSelectedAction(new_selected);
       return actions_view_->IsValidActionIndex(new_selected);
     }
     case ui::VKEY_RETURN: {
       int selected = actions_view_->selected_action();
@@ skipping 111 matching lines @@
                                     : SearchResult::Actions());
 }
 
 void SearchResultView::OnIsInstallingChanged() {
   const bool is_installing = result_ && result_->is_installing();
   actions_view_->SetVisible(!is_installing);
   progress_bar_->SetVisible(is_installing);
 }
 
 void SearchResultView::OnPercentDownloadedChanged() {
-  progress_bar_->SetValue(result_->percent_downloaded() / 100.0);
+  progress_bar_->SetValue(result_ ? result_->percent_downloaded() / 100.0 : 0);
 }
 
 void SearchResultView::OnItemInstalled() {
   delegate_->OnSearchResultInstalled(this);
 }
 
 void SearchResultView::OnItemUninstalled() {
   delegate_->OnSearchResultUninstalled(this);
 }
 
 void SearchResultView::OnSearchResultActionActivated(size_t index,
                                                      int event_flags) {
-  DCHECK(result_);
+  // |result_| could be NULL when result list is changing.
+  if (!result_)
+    return;
+
   DCHECK_LT(index, result_->actions().size());
 
   delegate_->SearchResultActionActivated(this, index, event_flags);
 }
 
 void SearchResultView::ShowContextMenuForView(views::View* source,
                                               const gfx::Point& point,
                                               ui::MenuSourceType source_type) {
-  ui::MenuModel* menu_model = result_->GetContextMenuModel();
+  ui::MenuModel* menu_model = result_ ? result_->GetContextMenuModel() : NULL;

[Matt Giuca, 2014/01/07 22:55:08]

Optional nit: It seems a little weird in the NULL case that it says:

menu_model = NULL
if (!menu_model)
  return;

Maybe more readable (if a little more verbose) like this:

if (!result_)
  return;
ui::MenuModel* menu_model = result_->GetContextMenuModel();
if (!menu_model)
  return;

[xiyuan, 2014/01/07 23:12:44]

Done.

   if (!menu_model)
     return;
 
   context_menu_runner_.reset(new views::MenuRunner(menu_model));
   if (context_menu_runner_->RunMenuAt(
           GetWidget(), NULL, gfx::Rect(point, gfx::Size()),
           views::MenuItemView::TOPLEFT, source_type,
           views::MenuRunner::HAS_MNEMONICS) ==
       views::MenuRunner::MENU_DELETED)
     return;
 }
 
 }  // namespace app_list