[Mac] Disable menu certain menu items when a modal dialog or sheet is present.

chrome/browser/cocoa/history_menu_cocoa_controller.mm

 // Copyright (c) 2010 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/cocoa/history_menu_cocoa_controller.h"
+
 #include "base/scoped_vector.h"
 #include "chrome/app/chrome_dll_resource.h"  // IDC_HISTORY_MENU
+#import "chrome/browser/app_controller_mac.h"
 #include "chrome/browser/browser.h"
-#import "chrome/browser/cocoa/history_menu_cocoa_controller.h"
-#include "chrome/browser/browser_list.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/cocoa/event_utils.h"
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "webkit/glue/window_open_disposition.h"
 
 @implementation HistoryMenuCocoaController
 
 - (id)initWithBridge:(HistoryMenuBridge*)bridge {
   if ((self = [super init])) {
     bridge_ = bridge;
     DCHECK(bridge_);
   }
   return self;
 }
 
+- (BOOL)validateMenuItem:(NSMenuItem*)menuItem {
+  AppController* controller = [NSApp delegate];
+  return [controller keyWindowIsNotModal];
+}
+
 // Open the URL of the given history item in the current tab.
 - (void)openURLForItem:(const HistoryMenuBridge::HistoryItem*)node {
   Browser* browser = Browser::GetOrCreateTabbedBrowser(bridge_->profile());
   WindowOpenDisposition disposition =
       event_utils::WindowOpenDispositionFromNSEvent([NSApp currentEvent]);
 
   // If this item can be restored using TabRestoreService, do so. Otherwise,
   // just load the URL.
   TabRestoreService* service = bridge_->profile()->GetTabRestoreService();
   if (node->session_id && service) {
     service->RestoreEntryById(browser, node->session_id, false);
   } else {
     DCHECK(node->url.is_valid());
     browser->OpenURL(node->url, GURL(), disposition,
                      PageTransition::AUTO_BOOKMARK);
   }
 }
 
 - (IBAction)openHistoryMenuItem:(id)sender {
   const HistoryMenuBridge::HistoryItem* item =
       bridge_->HistoryItemForMenuItem(sender);
   [self openURLForItem:item];
 }
 
 @end  // HistoryMenuCocoaController