Simplify the organization of //mojo_file_utils.

mojo/file_utils/lib/file_util.cc

-// Copyright 2015 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 "mojo/file_utils/file_util.h"
-
-#include <stdint.h>
-
-#include "mojo/services/files/interfaces/directory.mojom.h"
-#include "mojo/services/files/interfaces/file.mojom.h"
-#include "mojo/services/files/interfaces/types.mojom.h"
-
-namespace file_utils {
-
-mojo::files::FilePtr CreateTemporaryFileInDir(
-    mojo::files::DirectoryPtr* directory,
-    std::string* path_name) {
-  std::string internal_path_name;
-  const std::string charset("abcdefghijklmnopqrstuvwxyz1234567890");
-  const unsigned kSuffixLength = 6;
-  const unsigned kMaxNumAttempts = 10;
-  mojo::files::FilePtr temp_file;
-  mojo::files::Error error = mojo::files::Error::INTERNAL;
-  uint64_t random_value = 0;
-  for (unsigned attempt = 0; attempt < kMaxNumAttempts; attempt++) {
-    internal_path_name = ".org.chromium.Mojo.";
-    uint64_t microseconds = static_cast<uint64_t>(MojoGetTimeTicksNow());
-    for (unsigned i = 0; i < kSuffixLength; i++) {
-      // This roughly matches glibc's mapping from time to "random_time_bits",
-      // it seems to be good enough for creating temporary files.
-      random_value += (microseconds << 16) ^ (microseconds / 1000000);
-      internal_path_name.push_back(charset[random_value % charset.length()]);
-    }
-    (*directory)
-        ->OpenFile(internal_path_name, GetProxy(&temp_file),
-                   mojo::files::kOpenFlagWrite | mojo::files::kOpenFlagRead |
-                       mojo::files::kOpenFlagCreate |
-                       mojo::files::kOpenFlagExclusive,
-                   [&error](mojo::files::Error e) { error = e; });
-    if (!directory->WaitForIncomingResponse())
-      return nullptr;
-    // TODO(smklein): React to error code when ErrnoToError can return something
-    // other than Error::UNKNOWN. We only want to retry when "EEXIST" is thrown.
-    if (error == mojo::files::Error::OK) {
-      *path_name = internal_path_name;
-      return temp_file;
-    }
-  }
-  return nullptr;
-}
-
-}  // namespace file_utils