with sync

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 4708 matching lines @@
   // This happens during tests.
   if (!_webView) {
     return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
   }
 
   std::string MIMEType = self.webState->GetContentsMimeType();
   return [self documentTypeFromMIMEType:base::SysUTF8ToNSString(MIMEType)];
 }
 
 - (void)loadRequest:(NSMutableURLRequest*)request {
-  _latestWKNavigation.reset([[_webView loadRequest:request] retain]);
+  if ([[request URL] isFileURL]) {
+    NSURL* url = [request URL];
+    NSMutableArray* partsArray =
+        [NSMutableArray arrayWithArray:[url pathComponents]];
+    [partsArray removeLastObject];
+    _latestWKNavigation.reset([[_webView
+                    loadFileURL:url
+        allowingReadAccessToURL:[NSURL fileURLWithPathComponents:partsArray]]
+        retain]);
+  } else {
+    _latestWKNavigation.reset([[_webView loadRequest:request] retain]);
+  }
 }
 
 - (void)loadPOSTRequest:(NSMutableURLRequest*)request {
   if (!_POSTRequestLoader) {
     _POSTRequestLoader.reset([[CRWJSPOSTRequestLoader alloc] init]);
   }
 
   CRWWKScriptMessageRouter* messageRouter =
       [self webViewConfigurationProvider].GetScriptMessageRouter();
 
@@ skipping 905 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end