Use ScopedTaskEnvironment instead of MessageLoopForUI in components tests.

components/sync_sessions/favicon_cache_unittest.cc

Index: components/sync_sessions/favicon_cache_unittest.cc
diff --git a/components/sync_sessions/favicon_cache_unittest.cc b/components/sync_sessions/favicon_cache_unittest.cc
index 3db330f42abbedd1032093b32e78ef833e19b71b..19694452a517273836b781d6e004d7dd4a420c5a 100644
--- a/components/sync_sessions/favicon_cache_unittest.cc
+++ b/components/sync_sessions/favicon_cache_unittest.cc
@@ -5,11 +5,11 @@
 #include "components/sync_sessions/favicon_cache.h"
 
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/time/time.h"
 #include "components/sync/model/attachments/attachment_id.h"
 #include "components/sync/model/attachments/attachment_service_proxy_for_test.h"
@@ -258,7 +258,9 @@ int GetFaviconId(const syncer::SyncChange change) {
 
 class SyncFaviconCacheTest : public testing::Test {
  public:
-  SyncFaviconCacheTest();
+  SyncFaviconCacheTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
   ~SyncFaviconCacheTest() override {}
 
   void SetUpInitialSync(const syncer::SyncDataList& initial_image_data,
@@ -292,7 +294,7 @@ class SyncFaviconCacheTest : public testing::Test {
                                   int64_t last_visit_time_ms);
 
  private:
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   FaviconCache cache_;
 
   // Our dummy ChangeProcessor used to inspect changes pushed to Sync.