Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/fileapi/local_file_util_unittest.cc

Index: content/browser/fileapi/local_file_util_unittest.cc
diff --git a/content/browser/fileapi/local_file_util_unittest.cc b/content/browser/fileapi/local_file_util_unittest.cc
index 01962811924a01ab5c31082b3980981a16880ef9..548b90cbffd6539746c24e16e85373cf75d15cea 100644
--- a/content/browser/fileapi/local_file_util_unittest.cc
+++ b/content/browser/fileapi/local_file_util_unittest.cc
@@ -15,6 +15,7 @@
 #include "base/run_loop.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #include "build/build_config.h"
 #include "content/public/test/async_file_test_helper.h"
 #include "content/public/test/test_file_system_context.h"
@@ -121,7 +122,7 @@ class LocalFileUtilTest : public testing::Test {
   }
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   scoped_refptr<FileSystemContext> file_system_context_;
   base::ScopedTempDir data_dir_;