Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/fileapi/file_system_quota_client_unittest.cc

Index: content/browser/fileapi/file_system_quota_client_unittest.cc
diff --git a/content/browser/fileapi/file_system_quota_client_unittest.cc b/content/browser/fileapi/file_system_quota_client_unittest.cc
index 4cf1cf0bfce39284f2e1dcf5fb25fcec61e17ac4..b2f8c4f4e2e4895b9c7a28008a0448b8565f52ad 100644
--- a/content/browser/fileapi/file_system_quota_client_unittest.cc
+++ b/content/browser/fileapi/file_system_quota_client_unittest.cc
@@ -11,6 +11,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "content/public/test/async_file_test_helper.h"
 #include "content/public/test/test_file_system_context.h"
 #include "storage/browser/fileapi/file_system_context.h"
@@ -229,7 +230,7 @@ class FileSystemQuotaClientTest : public testing::Test {
   }
 
   base::ScopedTempDir data_dir_;
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   scoped_refptr<storage::FileSystemContext> file_system_context_;
   int64_t usage_;
   int additional_callback_count_;