Default constructor for file

webrtc/base/file.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/base/file.h"
 
 namespace rtc {
 
 File::File(PlatformFile file) : file_(file) {}
 
+File::File() : file_(kInvalidPlatformFileValue) {}
+
 File::~File() {
   Close();
 }
 
 File File::Open(const std::string& path) {
   return File(OpenPlatformFile(path));
 }
 
 File File::Create(const std::string& path) {
   return File(CreatePlatformFile(path));
 }
 
 File::File(File&& other) : file_(other.file_) {
   other.file_ = kInvalidPlatformFileValue;
 }
 
 File& File::operator=(File&& other) {
   Close();
   file_ = other.file_;
   other.file_ = kInvalidPlatformFileValue;
   return *this;
 }
 
 bool File::IsOpen() {
   return file_ != kInvalidPlatformFileValue;
 }
 
 }  // namespace rtc