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

ios/chrome/browser/ui/omnibox/omnibox_view_ios.h

 // Copyright (c) 2012 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.
 
 #ifndef IOS_CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_VIEW_IOS_H_
 #define IOS_CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_VIEW_IOS_H_
 
 #import <UIKit/UIKit.h>
 
 #include <memory>
@@ skipping 143 matching lines @@
   // voice search is not pending before attempting to process user actions that
   // may modify text field contents.
   // TODO(crbug.com/303212): Remove this workaround once the crash is fixed.
   bool ShouldIgnoreUserInputDueToPendingVoiceSearch();
 
   ios::ChromeBrowserState* browser_state_;
 
   base::scoped_nsobject<OmniboxTextFieldIOS> field_;
   WebOmniboxEditController* controller_;  // weak, owns us
   std::unique_ptr<OmniboxPopupViewIOS> popup_view_;
-  id<PreloadProvider> preloader_;
+  // |preloader_| should be __weak but is included from non-ARC code.
+  __unsafe_unretained id<PreloadProvider> preloader_;
 
   State state_before_change_;
   base::scoped_nsobject<NSString> marked_text_before_change_;
   NSRange current_selection_;
   NSRange old_selection_;
 
   // TODO(rohitrao): This is a monster hack, needed because closing the popup
   // ends up inadvertently triggering a new round of autocomplete.  Fix the
   // underlying problem, which is that textDidChange: is called when closing the
   // popup, and then remove this hack.  b/5877366.
   BOOL ignore_popup_updates_;
 
   // Bridges delegate method calls from |field_| to C++ land.
   base::scoped_nsobject<AutocompleteTextFieldDelegate> field_delegate_;
 
   // Temporary pointer to the attributed display string, stored as color and
   // other emphasis attributes are applied by the superclass.
   NSMutableAttributedString* attributing_display_string_;  // weak
 };
 
 #endif  // IOS_CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_VIEW_IOS_H_