Hide mac background mode prefs ui if background mode is not enabled.

chrome/browser/cocoa/preferences_window_controller.h

 // 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 <Cocoa/Cocoa.h>
 
 #include "base/scoped_ptr.h"
 #include "base/scoped_nsobject.h"
 #include "chrome/browser/options_window.h"
 #include "chrome/browser/prefs/pref_member.h"
@@ skipping 113 matching lines @@
   StringPrefMember autoOpenFiles_;
   BooleanPrefMember translateEnabled_;
   BooleanPrefMember tabsToLinks_;
   FontLanguageSettingsController* fontLanguageSettings_;
   StringPrefMember currentTheme_;
   IBOutlet NSButton* enableLoggingCheckbox_;
   scoped_ptr<PrefSetObserver> proxyPrefs_;
   BOOL proxiesConfigureButtonEnabled_;
   BOOL restoreButtonsEnabled_;
   BOOL restoreURLsEnabled_;
+  IBOutlet NSTextField* backgroundModeTitle_;
+  IBOutlet NSButton* backgroundModeCheckbox_;
+  IBOutlet NSTextField* backgroundModeDescription_;
+  IBOutlet NSButton* backgroundModeLearnMore_;
   BooleanPrefMember backgroundModeEnabled_;
 }
 
 // Designated initializer. |profile| should not be NULL.
 - (id)initWithProfile:(Profile*)profile initialPage:(OptionsPage)initialPage;
 
 // Show the preferences window.
 - (void)showPreferences:(id)sender;
 
 // Switch to the given preference page.
@@ skipping 64 matching lines @@
 
 // Returns the (normalized) page corresponding to the given toolbar item.
 // Should be called only after awakeFromNib is.
 - (OptionsPage)getPageForToolbarItem:(NSToolbarItem*)toolbarItem;
 
 // Returns the view corresponding to the given page.  Should be called
 // only after awakeFromNib is.
 - (NSView*)getPrefsViewForPage:(OptionsPage)page;
 
 @end