[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in ssl_errors

MessageLoop will go away, eventually.

BUG=891670

Change-Id: I297de47c1dd4d2a58276c136d8b48216ed4fd769
Reviewed-on: https://chromium-review.googlesource.com/c/1353889Reviewed-by: Carlos IL <carlosil@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#614388}

components/ssl_errors/error_classification_unittest.cc

@@ -7,13 +7,11 @@
 #include <memory>
 
 #include "base/files/file_path.h"
-#include "base/message_loop/message_loop.h"
 #include "base/strings/string_split.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/scoped_task_environment.h"
 #include "base/test/simple_test_clock.h"
 #include "base/test/simple_test_tick_clock.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/time/default_clock.h"
 #include "base/time/default_tick_clock.h"
 #include "components/network_time/network_time_test_utils.h"
@@ -254,7 +252,6 @@ TEST_F(SSLErrorClassificationTest, GetClockState) {
   histograms.ExpectTotalCount(kNetworkTimeHistogram, 0);
   TestingPrefServiceSimple pref_service;
   network_time::NetworkTimeTracker::RegisterPrefs(pref_service.registry());
-  base::MessageLoop loop;
   network_time::NetworkTimeTracker network_time_tracker(
       std::make_unique<base::DefaultClock>(),
       std::make_unique<base::DefaultTickClock>(), &pref_service,