Removed the code that checks the tab number.

chrome/browser/ui/cocoa/browser_window_controller.mm

 // Copyright (c) 2011 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/browser_window_controller.h"
 
 #include <Carbon/Carbon.h>
 
 #include "app/mac/scoped_nsdisable_screen_updates.h"
 #include "app/mac/nsimage_cache.h"
@@ skipping 989 matching lines @@
   SEL action = [item action];
   BOOL enable = NO;
   if (action == @selector(commandDispatch:) ||
       action == @selector(commandDispatchUsingKeyModifiers:)) {
     NSInteger tag = [item tag];
     if (browser_->command_updater()->SupportsCommand(tag)) {
       // Generate return value (enabled state)
       enable = browser_->command_updater()->IsCommandEnabled(tag);
       switch (tag) {
         case IDC_CLOSE_TAB:
-          // Disable "close tab" if we're not the key window or if there's only
-          // one tab.
-          enable &= [self numberOfTabs] > 1 && [[self window] isKeyWindow];
+          // Disable "close tab" if we're not the key window.
+          enable &= [[self window] isKeyWindow];
           break;
         case IDC_FULLSCREEN: {
           enable &= [self supportsFullscreen];
           if ([static_cast<NSObject*>(item) isKindOfClass:[NSMenuItem class]]) {
             NSString* menuTitle = l10n_util::GetNSString(
                 [self isFullscreen] ? IDS_EXIT_FULLSCREEN_MAC :
                                       IDS_ENTER_FULLSCREEN_MAC);
             [static_cast<NSMenuItem*>(item) setTitle:menuTitle];
           }
           break;
@@ skipping 1174 matching lines @@
 
 - (BOOL)supportsBookmarkBar {
   return [self supportsWindowFeature:Browser::FEATURE_BOOKMARKBAR];
 }
 
 - (BOOL)isTabbedWindow {
   return browser_->is_type_tabbed();
 }
 
 @end  // @implementation BrowserWindowController(WindowType)