[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in favicon

Use ScopedTaskEnvironment instead of MessageLoop in
favicon_service_impl_unittest.cc

MessageLoop will go away, eventually.

BUG=891670

Change-Id: I05f9b446058cdfe5e649e821fc8d87ac3e6ec764
Reviewed-on: https://chromium-review.googlesource.com/c/1352365Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#612441}

components/favicon/core/favicon_service_impl_unittest.cc

@@ -7,7 +7,7 @@
 #include <memory>
 
 #include "base/files/scoped_temp_dir.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/favicon/core/favicon_client.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/history/core/test/history_service_test_util.h"
@@ -17,7 +17,7 @@ namespace favicon {
 namespace {
 
 TEST(FaviconServiceImplTest, ShouldCacheUnableToDownloadFavicons) {
-  base::MessageLoop message_loop;
+  base::test::ScopedTaskEnvironment task_environment;
   base::ScopedTempDir history_dir;
   CHECK(history_dir.CreateUniqueTempDir());
   std::unique_ptr<history::HistoryService> history_service =