No need to pass DownloadItemModel ownership.

chrome/browser/download/download_shelf_context_menu.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 "chrome/browser/download/download_shelf_context_menu.h"
 
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/download/download_crx_util.h"
 #include "chrome/browser/download/download_item_model.h"
 #include "chrome/browser/download/download_prefs.h"
 #include "chrome/browser/safe_browsing/download_protection_service.h"
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/url_constants.h"
 #include "content/public/browser/download_item.h"
 #include "content/public/browser/download_manager.h"
 #include "content/public/browser/page_navigator.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
 using content::DownloadItem;
 using extensions::Extension;
 
-DownloadShelfContextMenu::~DownloadShelfContextMenu() {}
+DownloadShelfContextMenu::~DownloadShelfContextMenu() {
+  DetachFromDownloadItem();
+}
 
 DownloadShelfContextMenu::DownloadShelfContextMenu(
-    DownloadItemModel* download_model,
+    DownloadItem* download_item,
     content::PageNavigator* navigator)
-    : download_model_(download_model),
-      download_item_(download_model->download()),
+    : download_item_(download_item),
       navigator_(navigator) {
+  DCHECK(download_item_);
+  download_item_->AddObserver(this);
 }
 
 ui::SimpleMenuModel* DownloadShelfContextMenu::GetMenuModel() {
   ui::SimpleMenuModel* model = NULL;
+
+  if (!download_item_)
+    return NULL;
+
+  DownloadItemModel download_model(download_item_);
   // We shouldn't be opening a context menu for a dangerous download, unless it
   // is a malicious download.
-  DCHECK(!download_model_->IsDangerous() || download_model_->IsMalicious());
+  DCHECK(!download_model.IsDangerous() || download_model.IsMalicious());
 
-  if (download_model_->IsMalicious())
+  if (download_model.IsMalicious())
     model = GetMaliciousMenuModel();
   else if (download_item_->IsComplete())
     model = GetFinishedMenuModel();
   else if (download_item_->IsInterrupted())
     model = GetInterruptedMenuModel();
   else
     model = GetInProgressMenuModel();
   return model;
 }
 
 bool DownloadShelfContextMenu::IsCommandIdEnabled(int command_id) const {
+  if (!download_item_)
+    return false;
+
   switch (static_cast<ContextMenuCommands>(command_id)) {
     case SHOW_IN_FOLDER:
       return download_item_->CanShowInFolder() &&
           !download_item_->IsTemporary();
     case OPEN_WHEN_COMPLETE:
       return download_item_->CanShowInFolder() &&
           !download_item_->IsTemporary() &&
           (!download_crx_util::IsExtensionDownload(*download_item_) ||
            download_item_->IsComplete());
     case ALWAYS_OPEN_TYPE:
@@ skipping 10 matching lines @@
     case DISCARD:
     case KEEP:
     case LEARN_MORE_SCANNING:
     case LEARN_MORE_INTERRUPTED:
       return true;
   }
   return false;
 }
 
 bool DownloadShelfContextMenu::IsCommandIdChecked(int command_id) const {
+  if (!download_item_)
+    return false;
+
   switch (command_id) {
     case OPEN_WHEN_COMPLETE:
       return download_item_->GetOpenWhenComplete() ||
           download_crx_util::IsExtensionDownload(*download_item_);
     case ALWAYS_OPEN_TYPE:
       return download_item_->ShouldOpenFileBasedOnExtension();
     case TOGGLE_PAUSE:
       return download_item_->IsPaused();
   }
   return false;
 }
 
 void DownloadShelfContextMenu::ExecuteCommand(int command_id) {
+  if (!download_item_)
+    return;
+
   switch (static_cast<ContextMenuCommands>(command_id)) {
     case SHOW_IN_FOLDER:
       download_item_->ShowDownloadInShell();
       break;
     case OPEN_WHEN_COMPLETE:
       download_item_->OpenDownload();
       break;
     case ALWAYS_OPEN_TYPE: {
       DownloadPrefs* prefs = DownloadPrefs::FromBrowserContext(
           download_item_->GetBrowserContext());
       FilePath path = download_item_->GetUserVerifiedFilePath();
       if (!IsCommandIdChecked(ALWAYS_OPEN_TYPE))
         prefs->EnableAutoOpenBasedOnExtension(path);
       else
         prefs->DisableAutoOpenBasedOnExtension(path);
       break;
     }
     case CANCEL:
-      download_model_->CancelTask();
+      download_item_->Cancel(true /* Cancelled by user */);
       break;
     case TOGGLE_PAUSE:
       // It is possible for the download to complete before the user clicks the
       // menu item, recheck if the download is in progress state before toggling
       // pause.
       if (download_item_->IsPartialDownload())
         download_item_->TogglePause();
       break;
     case DISCARD:
       download_item_->Delete(DownloadItem::DELETE_DUE_TO_USER_DISCARD);
@@ skipping 38 matching lines @@
 
 bool DownloadShelfContextMenu::IsItemForCommandIdDynamic(int command_id) const {
   return command_id == TOGGLE_PAUSE;
 }
 
 string16 DownloadShelfContextMenu::GetLabelForCommandId(int command_id) const {
   switch (static_cast<ContextMenuCommands>(command_id)) {
     case SHOW_IN_FOLDER:
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_SHOW);
     case OPEN_WHEN_COMPLETE:
-      if (download_item_->IsInProgress())
+      if (download_item_ && download_item_->IsInProgress())
         return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_OPEN_WHEN_COMPLETE);
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_OPEN);
     case ALWAYS_OPEN_TYPE:
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_ALWAYS_OPEN_TYPE);
     case CANCEL:
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_CANCEL);
-    case TOGGLE_PAUSE: {
-      if (download_item_->IsPaused())
+    case TOGGLE_PAUSE:
+      if (download_item_ && download_item_->IsPaused())
         return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_RESUME_ITEM);
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_PAUSE_ITEM);
-    }
     case DISCARD:
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_DISCARD);
     case KEEP:
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_KEEP);
     case LEARN_MORE_SCANNING:
       return l10n_util::GetStringUTF16(IDS_DOWNLOAD_MENU_LEARN_MORE_SCANNING);
     case LEARN_MORE_INTERRUPTED:
       return l10n_util::GetStringUTF16(
           IDS_DOWNLOAD_MENU_LEARN_MORE_INTERRUPTED);
   }
   NOTREACHED();
   return string16();
 }
 
+void DownloadShelfContextMenu::DetachFromDownloadItem() {
+  if (!download_item_)
+    return;
+
+  download_item_->RemoveObserver(this);
+  download_item_ = NULL;
+}
+
+void DownloadShelfContextMenu::OnDownloadDestroyed(DownloadItem* download) {
+  DCHECK(download_item_ == download);
+  DetachFromDownloadItem();
+}
+
 ui::SimpleMenuModel* DownloadShelfContextMenu::GetInProgressMenuModel() {
   if (in_progress_download_menu_model_.get())
     return in_progress_download_menu_model_.get();
 
   in_progress_download_menu_model_.reset(new ui::SimpleMenuModel(this));
 
   in_progress_download_menu_model_->AddCheckItemWithStringId(
       OPEN_WHEN_COMPLETE, IDS_DOWNLOAD_MENU_OPEN_WHEN_COMPLETE);
   in_progress_download_menu_model_->AddCheckItemWithStringId(
       ALWAYS_OPEN_TYPE, IDS_DOWNLOAD_MENU_ALWAYS_OPEN_TYPE);
@@ skipping 57 matching lines @@
   malicious_download_menu_model_->AddItemWithStringId(
       DISCARD, IDS_DOWNLOAD_MENU_DISCARD);
   malicious_download_menu_model_->AddItemWithStringId(
       KEEP, IDS_DOWNLOAD_MENU_KEEP);
   malicious_download_menu_model_->AddSeparator(ui::NORMAL_SEPARATOR);
   malicious_download_menu_model_->AddItemWithStringId(
       LEARN_MORE_SCANNING, IDS_DOWNLOAD_MENU_LEARN_MORE_SCANNING);
 
   return malicious_download_menu_model_.get();
 }