No need to pass DownloadItemModel ownership.

chrome/browser/download/download_shelf_context_menu.cc

Index: chrome/browser/download/download_shelf_context_menu.cc
diff --git a/chrome/browser/download/download_shelf_context_menu.cc b/chrome/browser/download/download_shelf_context_menu.cc
index 3e13650a0082a45a96ec1f1d6439a3b37ea51444..0e70100524a593c6b1b253206ff1c754ce2d5ba2 100644
--- a/chrome/browser/download/download_shelf_context_menu.cc
+++ b/chrome/browser/download/download_shelf_context_menu.cc
@@ -21,23 +21,31 @@
 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();
@@ -49,6 +57,9 @@ ui::SimpleMenuModel* DownloadShelfContextMenu::GetMenuModel() {
 }
 
 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() &&
@@ -79,6 +90,9 @@ bool DownloadShelfContextMenu::IsCommandIdEnabled(int command_id) const {
 }
 
 bool DownloadShelfContextMenu::IsCommandIdChecked(int command_id) const {
+  if (!download_item_)
+    return false;
+
   switch (command_id) {
     case OPEN_WHEN_COMPLETE:
       return download_item_->GetOpenWhenComplete() ||
@@ -92,6 +106,9 @@ bool DownloadShelfContextMenu::IsCommandIdChecked(int command_id) const {
 }
 
 void DownloadShelfContextMenu::ExecuteCommand(int command_id) {
+  if (!download_item_)
+    return;
+
   switch (static_cast<ContextMenuCommands>(command_id)) {
     case SHOW_IN_FOLDER:
       download_item_->ShowDownloadInShell();
@@ -110,7 +127,7 @@ void DownloadShelfContextMenu::ExecuteCommand(int command_id) {
       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
@@ -169,18 +186,17 @@ string16 DownloadShelfContextMenu::GetLabelForCommandId(int command_id) const {
     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:
@@ -195,6 +211,19 @@ string16 DownloadShelfContextMenu::GetLabelForCommandId(int command_id) const {
   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();