Fixing std::swap(x, x) in base.

base/files/file.cc

 // Copyright (c) 2011 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/files/file.h"
 #include "base/files/file_path.h"
 #include "base/files/file_tracing.h"
 #include "base/metrics/histogram.h"
 #include "base/timer/elapsed_timer.h"
 #include "build/build_config.h"
@@ skipping 53 matching lines @@
 // static
 File File::CreateForAsyncHandle(PlatformFile platform_file) {
   File file(platform_file);
   // It would be nice if we could validate that |platform_file| was opened with
   // FILE_FLAG_OVERLAPPED on Windows but this doesn't appear to be possible.
   file.async_ = true;
   return file;
 }
 
 File& File::operator=(File&& other) {
-  DCHECK_NE(this, &other);
   Close();

[danakj, 2017/04/05 19:17:40]

I don't understand how this wouldn't close the file.

   SetPlatformFile(other.TakePlatformFile());
   tracing_path_ = other.tracing_path_;
   error_details_ = other.error_details();
   created_ = other.created();
   async_ = other.async_;
   return *this;
 }
 
 #if !defined(OS_NACL)
 void File::Initialize(const FilePath& path, uint32_t flags) {
@@ skipping 46 matching lines @@
       return "FILE_ERROR_IO";
     case FILE_ERROR_MAX:
       break;
   }
 
   NOTREACHED();
   return "";
 }
 
 }  // namespace base