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

ios/web/web_state/ui/crw_web_controller_container_view.mm

 // Copyright 2015 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_container_view.h"
 
 #include "base/ios/weak_nsobject.h"
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
 #import "ios/web/public/web_state/ui/crw_content_view.h"
@@ skipping 194 matching lines @@
 - (CRWWebViewProxyImpl*)contentViewProxy {
   return [_delegate contentViewProxyForContainerView:self];
 }
 
 - (CGRect)visibleFrame {
   CGFloat headerHeight = [_delegate headerHeightForContainerView:self];
   return UIEdgeInsetsInsetRect(self.bounds,
                                UIEdgeInsetsMake(headerHeight, 0, 0, 0));
 }
 
+- (id<CRWWebControllerContainerViewDelegate>)delegate {
+  return _delegate.get();
+}
+
+- (void)setDelegate:(id<CRWWebControllerContainerViewDelegate>)delegate {
+  _delegate.reset(delegate);
+}
+
 #pragma mark Layout
 
 - (void)layoutSubviews {
   [super layoutSubviews];
 
   self.webViewContentView.frame = self.bounds;
 
   // TODO(crbug.com/570114): Move adding of the following subviews to another
   // place.
 
@@ skipping 102 matching lines @@
   else
     self.toolbarContainerView = nil;
 }
 
 - (void)removeAllToolbars {
   // Resetting the property will remove the toolbars from the hierarchy.
   self.toolbarContainerView = nil;
 }
 
 @end