Remove isolated app code from iOS's chrome_browser_state_io_data.

ios/chrome/browser/browser_state/test_chrome_browser_state.mm

 // Copyright 2013 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 "ios/chrome/browser/browser_state/test_chrome_browser_state.h"
 
 #include <utility>
 
 #include "base/base_paths.h"
 #include "base/files/file_util.h"
@@ skipping 265 matching lines @@
     completion.Run();
 }
 
 net::URLRequestContextGetter* TestChromeBrowserState::CreateRequestContext(
     ProtocolHandlerMap* protocol_handlers,
     URLRequestInterceptorScopedVector request_interceptors) {
   return new net::TestURLRequestContextGetter(
       web::WebThread::GetTaskRunnerForThread(web::WebThread::IO));
 }
 
-net::URLRequestContextGetter*
-TestChromeBrowserState::CreateIsolatedRequestContext(
-    const base::FilePath& partition_path) {
-  return nullptr;
-}
-
 TestChromeBrowserState* TestChromeBrowserState::AsTestChromeBrowserState() {
   return this;
 }
 
 void TestChromeBrowserState::CreateWebDataService() {
   ignore_result(
       ios::WebDataServiceFactory::GetInstance()->SetTestingFactoryAndUse(
           this, &BuildWebDataService));
 
   // Wait a bit after creating the WebDataService to allow the initialisation
@@ skipping 115 matching lines @@
   DCHECK(!build_called_);
   pref_service_ = std::move(prefs);
 }
 
 scoped_ptr<TestChromeBrowserState> TestChromeBrowserState::Builder::Build() {
   DCHECK(!build_called_);
   return make_scoped_ptr(new TestChromeBrowserState(
       state_path_, std::move(pref_service_), testing_factories_,
       refcounted_testing_factories_));
 }