Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/bookmarks/bookmark_model_observer_for_cocoa.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 CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_MODEL_OBSERVER_FOR_COCOA_H_
+#define CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_MODEL_OBSERVER_FOR_COCOA_H_
+
+#import <Cocoa/Cocoa.h>
+
+#include <set>
+
+#include "base/mac/scoped_block.h"
+#include "base/macros.h"
+#include "components/bookmarks/browser/bookmark_model.h"
+#include "components/bookmarks/browser/bookmark_model_observer.h"
+
 // C++ bridge class to send a selector to a Cocoa object when the
 // bookmark model changes.  Some Cocoa objects edit the bookmark model
 // and temporarily save a copy of the state (e.g. bookmark button
 // editor).  As a fail-safe, these objects want an easy cancel if the
 // model changes out from under them.  For example, if you have the
 // bookmark button editor sheet open, then edit the bookmark in the
 // bookmark manager, we'd want to simply cancel the editor.
 //
 // This class is conservative and may result in notifications which
 // aren't strictly necessary.  For example, node removal only needs to
 // cancel an edit if the removed node is a folder (editors often have
 // a list of "new parents").  But, just to be sure, notification
 // happens on any removal.
-
-#ifndef CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_MODEL_OBSERVER_FOR_COCOA_H_
-#define CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_MODEL_OBSERVER_FOR_COCOA_H_
-
-#import <Cocoa/Cocoa.h>
-
-#include <set>
-
-#include "base/mac/scoped_block.h"
-#include "base/macros.h"
-#include "components/bookmarks/browser/bookmark_model.h"
-#include "components/bookmarks/browser/bookmark_model_observer.h"
-
 class BookmarkModelObserverForCocoa : public bookmarks::BookmarkModelObserver {
  public:
   // Callback called on a significant model change.
   typedef void (^ChangeCallback)();
 
   // When a |model| changes, or an observed node within it does, call a
   // |callback|.
   BookmarkModelObserverForCocoa(bookmarks::BookmarkModel* model,
                                 ChangeCallback callback);
   ~BookmarkModelObserverForCocoa() override;
@@ skipping 47 matching lines @@
       nodes_;  // Weak items owned by a BookmarkModel.
   base::mac::ScopedBlock<ChangeCallback> callback_;
 
   // Send a notification to the client.
   void Notify();
 
   DISALLOW_COPY_AND_ASSIGN(BookmarkModelObserverForCocoa);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_MODEL_OBSERVER_FOR_COCOA_H_