Revert of Use ScopedTaskEnvironment instead of MessageLoop in chrome unit tests.

chrome/utility/image_writer/image_writer_unittest.cc

 // Copyright 2014 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 <stdint.h>
 #include <string.h>
 
 #include <string>
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/run_loop.h"
-#include "base/test/scoped_task_environment.h"
 #include "chrome/utility/image_writer/error_messages.h"
 #include "chrome/utility/image_writer/image_writer.h"
 #include "chrome/utility/image_writer/image_writer_handler.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace image_writer {
 
 using testing::_;
 using testing::AnyNumber;
@@ skipping 23 matching lines @@
 
     ASSERT_TRUE(base::WriteFile(path, buffer.get(), kTestFileSize));
   }
 
   void FillDefault(const base::FilePath& path) { FillFile(path, kTestPattern); }
 
   base::FilePath image_path_;
   base::FilePath device_path_;
 
  private:
-  base::test::ScopedTaskEnvironment scoped_task_environment_;
+  base::MessageLoop message_loop_;
   base::ScopedTempDir temp_dir_;
 };
 
 class MockHandler : public ImageWriterHandler {
  public:
   MOCK_METHOD1(SendProgress, void(int64_t));
   MOCK_METHOD1(SendFailed, void(const std::string& message));
   MOCK_METHOD0(SendSucceeded, void());
 };
 
@@ skipping 157 matching lines @@
   EXPECT_CALL(mock_handler, SendFailed(_)).Times(0);
 
   FillDefault(image_path_);
 
   image_writer.Write();
 
   base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace image_writer