message: Fix the bug that LogStreamImpl locks the mutex twice.
diff: @@ -210,6 +210,8 @@ class LogStreamImpl {
  }
  private:
  + void ResetUnlocked();
  +
  // Real backing log stream.
  // This is not thread-safe so must be guarded.
  // If std::cerr is real log stream, this is empty.
  @@ -251,7 +253,7 @@ LogStreamImpl::LogStreamImpl() { Reset(); }
  // Others, false => true, initialized
  void LogStreamImpl::Init(const std::string &log_file_path) {
  absl::MutexLock l(&mutex_);
  - Reset();
  + ResetUnlocked();
  if (use_cerr_) {
  return;
  @@ -279,6 +281,10 @@ void LogStreamImpl::Init(const std::string &log_file_path) {
  void LogStreamImpl::Reset() {
  absl::MutexLock l(&mutex_);
  + ResetUnlocked();
  +}
  +
  +void LogStreamImpl::ResetUnlocked() {
  real_log_stream_.reset();
  config_verbose_level_ = 0;
  #if defined(OS_ANDROID) || defined(OS_WIN)
  