It's going to be removed from Chromium, see https://crbug.com/812523.

/cc @electron/code-owners 
shell/browser/api/electron_api_app.h
void OnGpuProcessCrashed(base::TerminationStatus status) override;
  
  void BrowserChildProcessLaunchedAndConnected(
      const content::ChildProcessData& data) override;
  void BrowserChildProcessHostDisconnected(
      const content::ChildProcessData& data) override;
  void BrowserChildProcessCrashed(
      const content::ChildProcessData& data,
      const content::ChildProcessTerminationInfo& info) override;
  void BrowserChildProcessKilled(
      const content::ChildProcessData& data,
      const content::ChildProcessTerminationInfo& info) override;
 private:
  void SetAppPath(const base::FilePath& app_path);
  void ChildProcessLaunched(int process_type, base::ProcessHandle handle);
  void ChildProcessDisconnected(base::ProcessId pid);
  void SetAppLogsPath(gin_helper::ErrorThrower thrower,
                      base::Optional<base::FilePath> custom_path);
  
  base::FilePath GetPath(gin_helper::ErrorThrower thrower,
                         const std::string& name);
  void SetPath(gin_helper::ErrorThrower thrower,
               const std::string& name,
               const base::FilePath& path);
  void SetDesktopName(const std::string& desktop_name);
  std::string GetLocale();
  std::string GetLocaleCountryCode();
  void OnSecondInstance(const base::CommandLine::StringVector& cmd,
                        const base::FilePath& cwd);
  bool HasSingleInstanceLock() const;