Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/fileapi/file_system_operation_runner_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <utility>
 
 #include "base/files/file_path.h"
 #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"
 #include "content/public/test/mock_special_storage_policy.h"
 #include "content/public/test/test_browser_thread_bundle.h"
 #include "content/public/test/test_file_system_context.h"
 #include "content/public/test/test_file_system_options.h"
 #include "storage/browser/fileapi/external_mount_points.h"
 #include "storage/browser/fileapi/file_system_backend.h"
 #include "storage/browser/fileapi/file_system_context.h"
@@ skipping 54 matching lines @@
         storage::kFileSystemTypeTemporary,
         base::FilePath::FromUTF8Unsafe(path));
   }
 
   FileSystemOperationRunner* operation_runner() {
     return file_system_context_->operation_runner();
   }
 
  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);
 };
 
 TEST_F(FileSystemOperationRunnerTest, NotFoundError) {
   bool done = false;
   base::File::Error status = base::File::FILE_ERROR_FAILED;
 
   // Regular NOT_FOUND error, which is called asynchronously.
@@ skipping 143 matching lines @@
   base::RunLoop run_loop;
   BrowserThread::PostTaskAndReply(
       BrowserThread::FILE, FROM_HERE,
       base::Bind(&base::DoNothing),
       run_loop.QuitClosure());
   run_loop.Run();
   // This should finish without thread assertion failure on debug build.
 }
 
 }  // namespace content