Fix Mac browser crash in BookmarkMenuBridge::UpdateMenu.

chrome/browser/cocoa/bookmark_menu_bridge.mm

 // Copyright (c) 2009 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.
 
 #import <AppKit/AppKit.h>
 
 #include "app/l10n_util.h"
 #include "app/resource_bundle.h"
 #include "base/nsimage_cache_mac.h"
 #include "base/sys_string_conversions.h"
@@ skipping 29 matching lines @@
 }
 
 void BookmarkMenuBridge::Loaded(BookmarkModel* model) {
   InvalidateMenu();
 }
 
 void BookmarkMenuBridge::UpdateMenu(NSMenu* bookmark_menu) {
   DCHECK(bookmark_menu);
   if (menuIsValid_)
     return;
+  BookmarkModel* model = GetBookmarkModel();
+  if (!model || !model->IsLoaded())
+    return;
 
   if (!folder_image_) {
     ResourceBundle& rb = ResourceBundle::GetSharedInstance();
     folder_image_.reset([rb.GetNSImageNamed(IDR_BOOKMARK_BAR_FOLDER) retain]);
   }
 
   ClearBookmarkMenu(bookmark_menu);
 
   // Add bookmark bar items, if any.
-  const BookmarkNode* barNode = GetBookmarkModel()->GetBookmarkBarNode();
+  const BookmarkNode* barNode = model->GetBookmarkBarNode();
+  CHECK(barNode);
   if (barNode->GetChildCount()) {
     [bookmark_menu addItem:[NSMenuItem separatorItem]];
     AddNodeToMenu(barNode, bookmark_menu);
   }
 
   // Create a submenu for "other bookmarks", and fill it in.
   NSString* other_items_title = base::SysWideToNSString(
     l10n_util::GetString(IDS_BOOMARK_BAR_OTHER_FOLDER_NAME));
   [bookmark_menu addItem:[NSMenuItem separatorItem]];
   AddNodeAsSubmenu(bookmark_menu,
-                   GetBookmarkModel()->other_node(),
+                   model->other_node(),
                    other_items_title);
 
   menuIsValid_ = true;
 }
 
 void BookmarkMenuBridge::BookmarkModelBeingDeleted(BookmarkModel* model) {
   NSMenu* bookmark_menu = BookmarkMenu();
   if (bookmark_menu == nil)
     return;
 
@@ skipping 151 matching lines @@
 
 NSMenuItem* BookmarkMenuBridge::MenuItemForNode(const BookmarkNode* node) {
   if (!node)
     return nil;
   std::map<const BookmarkNode*, NSMenuItem*>::iterator it =
       bookmark_nodes_.find(node);
   if (it == bookmark_nodes_.end())
     return nil;
   return it->second;
 }