Base: Copy platform_file.* to files/file.*

base/files/file_unittest.cc

 // Copyright (c) 2012 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 "base/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/platform_file.h"
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 414 matching lines @@
                 file, buffer, first_chunk_size));
   EXPECT_EQ(kDataSize - first_chunk_size,
             base::ReadPlatformFileAtCurrentPos(
                 file, buffer + first_chunk_size,
                 kDataSize - first_chunk_size));
   EXPECT_EQ(std::string(buffer, buffer + kDataSize),
             std::string(kData));
 
   base::ClosePlatformFile(file);
 }