[Mac] Inform reference counted objects that hold a weak Browser* when the Browser is being destroye…

chrome/browser/ui/cocoa/bookmarks/bookmark_bar_controller.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.
 
 #import "chrome/browser/ui/cocoa/bookmarks/bookmark_bar_controller.h"
 
 #include "base/mac/bundle_locations.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 282 matching lines @@
             initWithBookmarkBarController:self]);
 
     // This call triggers an -awakeFromNib, which builds the bar, which might
     // use |folderImage_| and |contextMenuController_|. Ensure it happens after
     // |folderImage_| is loaded and |contextMenuController_| is created.
     [[self animatableView] setResizeDelegate:resizeDelegate];
   }
   return self;
 }
 
+- (void)browserWillBeDestroyed {
+  browser_ = nullptr;
+}
+
 - (Browser*)browser {
   return browser_;
 }
 
 - (BookmarkContextMenuCocoaController*)menuController {
   return contextMenuController_.get();
 }
 
 - (void)pulseBookmarkNotification:(NSNotification*)notification {
   NSDictionary* dict = [notification userInfo];
@@ skipping 2589 matching lines @@
 - (id<BookmarkButtonControllerProtocol>)controllerForNode:
     (const BookmarkNode*)node {
   // See if it's in the bar, then if it is in the hierarchy of visible
   // folder menus.
   if (bookmarkModel_->bookmark_bar_node() == node)
     return self;
   return [folderController_ controllerForNode:node];
 }
 
 @end