mandoline filesystem: Rewrite using base::File.

components/filesystem/file_system_impl.h

 // 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.
 
 #ifndef COMPONENTS_FILESYSTEM_FILE_SYSTEM_IMPL_H_
 #define COMPONENTS_FILESYSTEM_FILE_SYSTEM_IMPL_H_
 
 #include "base/macros.h"
 #include "components/filesystem/public/interfaces/file_system.mojom.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
@@ skipping 13 matching lines @@
 
   // |Files| implementation:
   // We provide a "private" temporary file system as the default. In Debug
   // builds, we also provide access to a common file system named "debug"
   // (stored under ~/MojoDebug).
   void OpenFileSystem(const mojo::String& file_system,
                       mojo::InterfaceRequest<Directory> directory,
                       const OpenFileSystemCallback& callback) override;
 
  private:
+  const std::string remote_application_url_;
   mojo::StrongBinding<FileSystem> binding_;
 
   DISALLOW_COPY_AND_ASSIGN(FileSystemImpl);
 };
 
 }  // namespace filesystem
 
 #endif  // COMPONENTS_FILESYSTEM_FILE_SYSTEM_IMPL_H_