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

/cc @electron/code-owners 
shell/browser/api/electron_api_app.h
content::WebContents* web_contents,
      int cert_error,
      const net::SSLInfo& ssl_info,
      const GURL& request_url,
      bool is_main_frame_request,
      bool strict_enforcement,
      base::OnceCallback<void(content::CertificateRequestResultType)> callback)
      override;
  base::OnceClosure SelectClientCertificate(
      content::WebContents* web_contents,
      net::SSLCertRequestInfo* cert_request_info,
      net::ClientCertIdentityList client_certs,
      std::unique_ptr<content::ClientCertificateDelegate> delegate) override;
  bool CanCreateWindow(content::RenderFrameHost* opener,
                       const GURL& opener_url,
                       const GURL& opener_top_level_frame_url,
                       const url::Origin& source_origin,
                       content::mojom::WindowContainerType container_type,
                       const GURL& target_url,
                       const content::Referrer& referrer,
                       const std::string& frame_name,
                       WindowOpenDisposition disposition,
                       const blink::mojom::WindowFeatures& features,
                       const std::string& raw_features,
                       const scoped_refptr<network::ResourceRequestBody>& body,
                       bool user_gesture,
                       bool opener_suppressed,
                       bool* no_javascript_access) override;
  
  void OnGpuInfoUpdate() override;