Mac: Fix BMB commands triggering a standalone window instead of a sheet.

chrome/browser/ui/cocoa/bookmarks/bookmark_context_menu_cocoa_controller.mm

 // Copyright (c) 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.
 
 #import "chrome/browser/ui/cocoa/bookmarks/bookmark_context_menu_cocoa_controller.h"
 
 #include <vector>
 
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
@@ skipping 70 matching lines @@
   menuController_.reset([[MenuController alloc] initWithModel:menuModel
                                        useWithPopUpButtonCell:NO]);
 }
 
 - (NSMenu*)menuForBookmarkNode:(const BookmarkNode*)node {
   // Depending on timing, the model may not yet have been loaded.
   BookmarkModel* bookmarkModel = [bookmarkBarController_ bookmarkModel];
   if (!bookmarkModel || !bookmarkModel->IsLoaded())
     return nil;
 
+  // This may be called before the BMB view has been added to the window. In
+  // that case, simply return nil so that BookmarkContextMenuController doesn't
+  // get created with a nil window.
+  if (![bookmarkBarController_ browserWindow])
+    return nil;
+
   if (!node)
     node = bookmarkModel->bookmark_bar_node();
 
   // Rebuild the menu if it's for a different node than the last request.
   if (!menuController_ || node != bookmarkNode_) {
     bookmarkNode_ = node;
     [self createMenuControllers:bookmarkModel];
   }
   return [menuController_ menu];
 }
@@ skipping 10 matching lines @@
 
   [bookmarkBarController_ closeFolderAndStopTrackingMenus];
   [bookmarkBarController_ unhighlightBookmark:bookmarkNode_];
 }
 
 - (void)cancelTracking {
   [[menuController_ menu] cancelTracking];
 }
 
 @end