Use ScopedTaskEnvironment instead of MessageLoop in components unit tests.

components/omnibox/browser/zero_suggest_provider_unittest.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 "components/omnibox/browser/zero_suggest_provider.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/history/core/browser/top_sites.h"
 #include "components/metrics/proto/omnibox_event.pb.h"
 #include "components/omnibox/browser/autocomplete_provider_listener.h"
 #include "components/omnibox/browser/mock_autocomplete_provider_client.h"
 #include "components/omnibox/browser/omnibox_field_trial.h"
 #include "components/omnibox/browser/omnibox_pref_names.h"
 #include "components/omnibox/browser/test_scheme_classifier.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/search_engines/template_url.h"
@@ skipping 137 matching lines @@
 
  protected:
   // AutocompleteProviderListener:
   void OnProviderUpdate(bool updated_matches) override;
 
   void ResetFieldTrialList();
 
   void CreatePersonalizedFieldTrial();
   void CreateMostVisitedFieldTrial();
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 
   // Needed for OmniboxFieldTrial::ActivateStaticTrials().
   std::unique_ptr<base::FieldTrialList> field_trial_list_;
 
   net::TestURLFetcherFactory test_factory_;
   std::unique_ptr<FakeAutocompleteProviderClient> client_;
   scoped_refptr<ZeroSuggestProvider> provider_;
   TemplateURL* default_t_url_;
 
  private:
@@ skipping 262 matching lines @@
 
   base::RunLoop().RunUntilIdle();
 
   // Expect that the matches have been cleared.
   ASSERT_TRUE(provider_->matches().empty());
 
   // Expect the new results have been stored.
   EXPECT_EQ(empty_response,
             prefs->GetString(omnibox::kZeroSuggestCachedResults));
 }