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

chrome/browser/ui/cocoa/toolbar/back_forward_menu_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/toolbar/back_forward_menu_controller.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/sys_string_conversions.h"
 #import "chrome/browser/ui/cocoa/menu_button.h"
@@ skipping 22 matching lines @@
     backForwardMenu_.reset([[NSMenu alloc] initWithTitle:@""]);
     DCHECK(backForwardMenu_.get());
     [backForwardMenu_ setDelegate:self];
 
     [button_ setAttachedMenu:backForwardMenu_];
     [button_ setOpenMenuOnClick:NO];
   }
   return self;
 }
 
+- (void)browserWillBeDestroyed {
+  [button_ setAttachedMenu:nil];
+  [backForwardMenu_ setDelegate:nil];
+  backForwardMenu_.reset();
+  model_.reset();
+}
+
 // Methods as delegate:
 
 // Called by backForwardMenu_ just before tracking begins.
 //TODO(viettrungluu): should we do anything for chapter stops (see model)?
 - (void)menuNeedsUpdate:(NSMenu*)menu {
   DCHECK(menu == backForwardMenu_);
 
   // Remove old menu items (backwards order is as good as any).
   for (NSInteger i = [menu numberOfItems]; i > 0; i--)
     [menu removeItemAtIndex:(i - 1)];
@@ skipping 37 matching lines @@
 // Action methods:
 
 - (void)executeMenuItem:(id)sender {
   DCHECK([sender isKindOfClass:[NSMenuItem class]]);
   int menuID = [sender tag];
   int event_flags = ui::EventFlagsFromNative([NSApp currentEvent]);
   model_->ActivatedAt(menuID, event_flags);
 }
 
 @end  // @implementation BackForwardMenuController