Reload offline version on load failure

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 3458 matching lines @@
     CRWSessionEntry* currentEntry = [self currentSessionEntry];
     // TODO(crbug.com/570699): Remove this check once it's no longer possible to
     // have no current entries.
     if (currentEntry)
       [self cachePOSTDataForRequest:request inSessionEntry:currentEntry];
   }
 
   return YES;
 }
 
+- (void)displayOfflineVersionForURL:(const GURL&)URL {
+  if ([_nativeProvider hasControllerForURL:URL]) {
+    id<CRWNativeContent> controller = [_nativeProvider controllerForURL:URL];
+    web::NavigationItem* item =
+        self.webState->GetNavigationManager()->GetItemAtIndex(
+            self.webState->GetNavigationManager()->GetCurrentItemIndex());
+    // Allows the native content to set the displayed URL.
+    if (item) {
+      item->SetURL([controller url]);
+      if ([controller respondsToSelector:@selector(virtualURL)]) {
+        item->SetVirtualURL([controller virtualURL]);
+      }
+    }
+    [self loadCompleteWithSuccess:NO];
+    [self removeWebViewAllowingCachedReconstruction:NO];
+    [self setNativeController:controller];
+    [self loadNativeViewWithSuccess:YES];
+  }
+}
+
 - (void)handleLoadError:(NSError*)error inMainFrame:(BOOL)inMainFrame {
   NSString* MIMEType = [_pendingNavigationInfo MIMEType];
   if ([_passKitDownloader isMIMETypePassKitType:MIMEType])
     return;
   if ([error code] == NSURLErrorUnsupportedURL)
     return;
   // In cases where a Plug-in handles the load do not take any further action.
   if ([error.domain isEqual:base::SysUTF8ToNSString(web::kWebKitErrorDomain)] &&
       (error.code == web::kWebKitErrorPlugInLoadFailed ||
        error.code == web::kWebKitErrorCannotShowUrl))
@@ skipping 2303 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end