Added |-cancelJavaScriptDialogsForWebController:| to UI delegate.

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 <objc/runtime.h>
 #include <cmath>
 
 #include "base/ios/block_types.h"
@@ skipping 673 matching lines @@
 
 - (NSString*)scriptByAddingWindowIDCheckForScript:(NSString*)script {
   NSString* kTemplate = @"if (__gCrWeb['windowId'] === '%@') { %@; }";
   return [NSString stringWithFormat:kTemplate, [self windowId], script];
 }
 
 - (void)removeWebViewAllowingCachedReconstruction:(BOOL)allowCache {
   if (!self.webView)
     return;
 
+  SEL cancelDialogsSelector =
+      @selector(cancelJavaScriptDialogsForWebController:);
+  if ([self.UIDelegate respondsToSelector:cancelDialogsSelector])
+    [self.UIDelegate cancelJavaScriptDialogsForWebController:self];
+
   if (allowCache)
     _expectedReconstructionURL = [self currentNavigationURL];
   else
     _expectedReconstructionURL = GURL();
 
   [self abortLoad];
   [self.webView removeFromSuperview];
   [self.containerView resetContent];
   [self resetWebView];
 }
@@ skipping 3162 matching lines @@
   if ([MIMEType isEqualToString:@"text/html"] ||
       [MIMEType isEqualToString:@"application/xhtml+xml"] ||
       [MIMEType isEqualToString:@"application/xml"]) {
     return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 @end