[Mac] Refactor bookmark bar controller

chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm

 // 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.
 
 #include "chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.h"
 
 #include "base/bind.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/cocoa/bookmarks/bookmark_bar_controller.h"
 #include "components/bookmarks/browser/bookmark_model.h"
@@ skipping 32 matching lines @@
 BookmarkBarBridge::~BookmarkBarBridge() {
   if (model_)
     model_->RemoveObserver(this);
 }
 
 void BookmarkBarBridge::BookmarkModelLoaded(BookmarkModel* model,
                                             bool ids_reassigned) {
   [controller_ loaded:model];
 }
 
 void BookmarkBarBridge::BookmarkModelBeingDeleted(BookmarkModel* model) {

[Elly Fong-Jones, 2017/03/23 15:40:21]

can this happen in other circumstances than the browser being torn down?

-  [controller_ beingDeleted:model];
   model_->RemoveObserver(this);
   model_ = nullptr;
+  // The browser may be being torn down; little is safe to do.  As an
+  // example, it may not be safe to clear the pasteboard.
+  // http://crbug.com/38665
 }
 
 void BookmarkBarBridge::BookmarkNodeMoved(BookmarkModel* model,
                                           const BookmarkNode* old_parent,
                                           int old_index,
                                           const BookmarkNode* new_parent,
                                           int new_index) {
   if (!batch_mode_) {
     [controller_ nodeMoved:model
                  oldParent:old_parent oldIndex:old_index
@@ skipping 48 matching lines @@
 }
 
 void BookmarkBarBridge::ExtensiveBookmarkChangesEnded(BookmarkModel* model) {
   batch_mode_ = false;
   [controller_ loaded:model];
 }
 
 void BookmarkBarBridge::OnExtraButtonsVisibilityChanged() {
   [controller_ updateExtraButtonsVisibility];
 }