[ObjC ARC] Converts ios/chrome/browser/ui/bookmarks:bookmarks to ARC.

ios/chrome/browser/ui/bookmarks/bookmark_navigation_controller.mm

 // Copyright 2014 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 "ios/chrome/browser/ui/bookmarks/bookmark_navigation_controller.h"
 
-#include "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/ui/bookmarks/bookmark_utils_ios.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation BookmarkNavigationController
 
 - (id)initWithRootViewController:(UIViewController*)rootViewController {
   self = [super initWithRootViewController:rootViewController];
   if (self) {
     [self setNavigationBarHidden:YES];
   }
   return self;
 }
 
 - (void)viewDidLoad {
   [super viewDidLoad];
   self.view.backgroundColor = [UIColor whiteColor];
 }
 
 - (BOOL)disablesAutomaticKeyboardDismissal {
   // This allows us to hide the keyboard when controllers are being displayed in
   // a modal form sheet on the iPad.
   return NO;
 }
 
 #pragma mark - UIResponder
 
 - (BOOL)canBecomeFirstResponder {
   return YES;
 }
 
 @end