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

chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_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 <Cocoa/Cocoa.h>
 
 #include "base/auto_reset.h"
 #include "base/mac/bundle_locations.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/ui/browser_finder.h"
@@ skipping 69 matching lines @@
     [[NSNotificationCenter defaultCenter]
         addObserver:self
            selector:@selector(findPboardUpdated:)
                name:kFindPasteboardChangedNotification
              object:[FindPasteboard sharedInstance]];
     browser_ = browser;
   }
   return self;
 }
 
-- (void)dealloc {
+- (void)browserWillBeDestroyed {
   // All animations should have been explicitly stopped before a tab is closed.
   DCHECK(!showHideAnimation_.get());
   DCHECK(!moveAnimation_.get());
   [[NSNotificationCenter defaultCenter] removeObserver:self];
-  [super dealloc];
+  browser_ = nullptr;
 }
 
 - (void)setFindBarBridge:(FindBarBridge*)findBarBridge {
   DCHECK(!findBarBridge_);  // should only be called once.
   findBarBridge_ = findBarBridge;
 }
 
 - (void)awakeFromNib {
   [[closeButton_ cell] setImageID:IDR_CLOSE_1
                    forButtonState:image_button_cell::kDefaultState];
@@ skipping 509 matching lines @@
 }
 
 - (BrowserWindowController*)browserWindowController {
   if (!browser_)
     return nil;
   return [BrowserWindowController
       browserWindowControllerForWindow:browser_->window()->GetNativeWindow()];
 }
 
 @end