Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/fileapi/file_system_operation_runner_unittest.cc

Index: content/browser/fileapi/file_system_operation_runner_unittest.cc
diff --git a/content/browser/fileapi/file_system_operation_runner_unittest.cc b/content/browser/fileapi/file_system_operation_runner_unittest.cc
index 0e9a0c2c2da1332dd562832a8d06e07317bfdb11..7c2f17450a459b2e4bd2b83de5a0b2a4184efe70 100644
--- a/content/browser/fileapi/file_system_operation_runner_unittest.cc
+++ b/content/browser/fileapi/file_system_operation_runner_unittest.cc
@@ -8,6 +8,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "content/public/browser/browser_thread.h"
@@ -82,7 +83,7 @@ class FileSystemOperationRunnerTest : public testing::Test {
 
  private:
   base::ScopedTempDir base_;
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   scoped_refptr<FileSystemContext> file_system_context_;
 
   DISALLOW_COPY_AND_ASSIGN(FileSystemOperationRunnerTest);