Convert SupervisedUserResourceThrottle to a NavigationThrottle.

chrome/browser/supervised_user/supervised_user_interstitial.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/supervised_user/supervised_user_interstitial.h"
 
 #include <stddef.h>
 
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 292 matching lines @@
           << (success ? " successfully" : " unsuccessfully");
   std::string jsFunc =
       base::StringPrintf("setRequestStatus(%s);", success ? "true" : "false");
   interstitial_page_->GetMainFrame()->ExecuteJavaScript(
       base::ASCIIToUTF16(jsFunc));
 }
 
 bool SupervisedUserInterstitial::ShouldProceed() {
   SupervisedUserService* supervised_user_service =
       SupervisedUserServiceFactory::GetForProfile(profile_);
-  SupervisedUserURLFilter* url_filter =
-      supervised_user_service->GetURLFilterForUIThread();
+  const SupervisedUserURLFilter* url_filter =
+      supervised_user_service->GetURLFilter();
   SupervisedUserURLFilter::FilteringBehavior behavior;
   if (url_filter->HasAsyncURLChecker()) {
     if (!url_filter->GetManualFilteringBehaviorForURL(url_, &behavior))
       return false;
   } else {
     behavior = url_filter->GetFilteringBehaviorForURL(url_);
   }
   return behavior != SupervisedUserURLFilter::BLOCK;
 }
 
@@ skipping 22 matching lines @@
       SupervisedUserServiceFactory::GetForProfile(profile_);
   supervised_user_service->RemoveObserver(this);
 
   if (!callback_.is_null())
     callback_.Run(continue_request);
 
   // After this, the WebContents may be destroyed. Make sure we don't try to use
   // it again.
   web_contents_ = nullptr;
 }