[Mac] Nil out content shell window delegate on close

content/shell/browser/shell_mac.mm

 // Copyright 2013 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 "content/shell/browser/shell.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
+#import "base/mac/foundation_util.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/sys_string_conversions.h"
 #include "content/public/browser/native_web_keyboard_event.h"
 #include "content/public/browser/web_contents.h"
 #include "content/shell/app/resource.h"
 #import "ui/base/cocoa/underlay_opengl_hosting_window.h"
 #include "url/gurl.h"
 
@@ skipping 12 matching lines @@
   if ((self = [super init])) {
     shell_ = shell;
   }
   return self;
 }
 
 // Called when the window is about to close. Perform the self-destruction
 // sequence by getting rid of the shell and removing it and the window from
 // the various global lists. By returning YES, we allow the window to be
 // removed from the screen.
-- (BOOL)windowShouldClose:(id)window {
+- (BOOL)windowShouldClose:(id)sender {
+  NSWindow* window = base::mac::ObjCCastStrict<NSWindow>(sender);
   [window autorelease];
+  // Don't leave a dangling pointer if the window lives beyond
+  // this method. See crbug.com/719830.
+  [window setDelegate:nil];
   delete shell_;
   [self release];
 
   return YES;
 }
 
 - (void)performAction:(id)sender {
   shell_->ActionPerformed([sender tag]);
 }
 
@@ skipping 265 matching lines @@
         [[event.os_event characters] isEqual:@"l"]) {
       [window_ makeFirstResponder:url_edit_view_];
       return;
     }
 
     [[NSApp mainMenu] performKeyEquivalent:event.os_event];
   }
 }
 
 }  // namespace content