Show singleton tab instead of opening multiple help tabs.

chrome/browser/app_controller_mac.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/app_controller_mac.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/mac/foundation_util.h"
@@ skipping 806 matching lines @@
         Browser::OpenDownloadsWindow(lastProfile);
       break;
     case IDC_MANAGE_EXTENSIONS:
       if (Browser* browser = ActivateBrowser(lastProfile))
         browser->ShowExtensionsTab();
       else
         Browser::OpenExtensionsWindow(lastProfile);
       break;
     case IDC_HELP_PAGE:
       if (Browser* browser = ActivateBrowser(lastProfile))
-        browser->OpenHelpTab();
+        browser->ShowHelpTab();
       else
         Browser::OpenHelpWindow(lastProfile);
       break;
     case IDC_FEEDBACK: {
       Browser* browser = BrowserList::GetLastActive();
       TabContents* currentTab =
           browser ? browser->GetSelectedTabContents() : NULL;
       BugReportWindowController* controller =
           [[BugReportWindowController alloc]
               initWithTabContents:currentTab
@@ skipping 358 matching lines @@
 
 }  // namespace browser
 
 namespace app_controller_mac {
 
 bool IsOpeningNewWindow() {
   return g_is_opening_new_window;
 }
 
 }  // namespace app_controller_mac