Remove calls to deprecated MessageLoop methods in ios.

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 342 matching lines @@
   return true;
 }
 
 void TestChromeBrowserState::DestroyHistoryService() {
   history::HistoryService* history_service =
       ios::HistoryServiceFactory::GetInstance()->GetForBrowserStateIfExists(
           this, ServiceAccessType::EXPLICIT_ACCESS);
   if (!history_service)
     return;
 
+  base::RunLoop run_loop;
+
   history_service->ClearCachedDataForContextID(0);
-  history_service->SetOnBackendDestroyTask(
-      base::MessageLoop::QuitWhenIdleClosure());
+  history_service->SetOnBackendDestroyTask(run_loop.QuitWhenIdleClosure());
   history_service->Shutdown();
   history_service = nullptr;
 
   // Resetting the testing factory force the destruction of the current
   // HistoryService instance associated with the TestChromeBrowserState.
   ios::HistoryServiceFactory::GetInstance()->SetTestingFactory(this, nullptr);
 
   // Wait for the backend class to terminate before deleting the files and
   // moving to the next test. Note: if this never terminates, somebody is
   // probably leaking a reference to the history backend, so it never calls
   // our destroy task.
-  base::MessageLoop::current()->Run();
-
-  // Make sure we don't have any event pending that could disrupt the next
-  // test.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::MessageLoop::QuitWhenIdleClosure());
-  base::MessageLoop::current()->Run();
+  run_loop.Run();
 }
 
 syncable_prefs::TestingPrefServiceSyncable*
 TestChromeBrowserState::GetTestingPrefService() {
   DCHECK(prefs_);
   DCHECK(testing_prefs_);
   return testing_prefs_;
 }
 
 TestChromeBrowserState::Builder::Builder() : build_called_(false) {}
@@ skipping 25 matching lines @@
   pref_service_ = std::move(prefs);
 }
 
 std::unique_ptr<TestChromeBrowserState>
 TestChromeBrowserState::Builder::Build() {
   DCHECK(!build_called_);
   return base::WrapUnique(new TestChromeBrowserState(
       state_path_, std::move(pref_service_), testing_factories_,
       refcounted_testing_factories_));
 }