Zero-out crw_web_controller's container view delegate in dealloc.

ios/web/web_state/ui/crw_web_controller.mm

 // Copyright 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 "ios/web/web_state/ui/crw_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #import <objc/runtime.h>
 #include <stddef.h>
@@ skipping 1096 matching lines @@
 }
 
 - (void)setUIDelegate:(id<CRWWebUserInterfaceDelegate>)UIDelegate {
   _UIDelegate.reset(UIDelegate);
 }
 
 - (void)dealloc {
   DCHECK([NSThread isMainThread]);
   DCHECK(_isBeingDestroyed);  // 'close' must have been called already.
   DCHECK(!_webView);
+  [_containerView setDelegate:nil];

[Eugene But (OOO till 7-30), 2016/10/25 18:24:34]

Is this change temporary? If so, could you please add TODO to remove it.
Otherwise could you please add a comment which explains why this is necessary.

   _touchTrackingRecognizer.get().touchTrackingDelegate = nil;
   [[_webViewProxy scrollViewProxy] removeObserver:self];
   [[NSNotificationCenter defaultCenter] removeObserver:self];
   [super dealloc];
 }
 
 - (void)dismissKeyboard {
   [_webView endEditing:YES];
   if ([self.nativeController respondsToSelector:@selector(dismissKeyboard)])
     [self.nativeController dismissKeyboard];
@@ skipping 4521 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end