Revert of Move file_handlers API from //chrome to //extensions

extensions/browser/api/file_handlers/directory_util.h

-// Copyright 2016 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.
-
-#ifndef EXTENSIONS_BROWSER_API_FILE_HANDLERS_DIRECTORY_UTIL_H_
-#define EXTENSIONS_BROWSER_API_FILE_HANDLERS_DIRECTORY_UTIL_H_
-
-#include <memory>
-#include <set>
-#include <string>
-#include <vector>
-
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/memory/weak_ptr.h"
-
-namespace content {
-class BrowserContext;
-}
-
-namespace base {
-class FilePath;
-}  // namespace base
-
-namespace extensions {
-namespace app_file_handler_util {
-
-class IsDirectoryCollector {
- public:
-  typedef base::Callback<void(std::unique_ptr<std::set<base::FilePath>>)>
-      CompletionCallback;
-
-  explicit IsDirectoryCollector(content::BrowserContext* context);
-  virtual ~IsDirectoryCollector();
-
-  // For the given paths obtains a set with which of them are directories.
-  // The collector does not support virtual files if OS != CHROMEOS.
-  void CollectForEntriesPaths(const std::vector<base::FilePath>& paths,
-                              const CompletionCallback& callback);
-
- private:
-  void OnIsDirectoryCollected(size_t index, bool directory);
-
-  content::BrowserContext* context_;
-  std::vector<base::FilePath> paths_;
-  std::unique_ptr<std::set<base::FilePath>> result_;
-  size_t left_;
-  CompletionCallback callback_;
-  base::WeakPtrFactory<IsDirectoryCollector> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(IsDirectoryCollector);
-};
-
-}  // namespace app_file_handler_util
-}  // namespace extensions
-
-#endif  // EXTENSIONS_BROWSER_API_FILE_HANDLERS_DIRECTORY_UTIL_H_