Make browser window optional

docs/api/dialog.md

@@ -175,9 +175,9 @@ it is usually used to report errors in early stage of startup.  If called
 before the app `ready`event on Linux, the message will be emitted to stderr,
 and no GUI dialog will appear.
 
-### `dialog.showCertificateTrustDialog(browserWindow, options, callback)` _macOS_
+### `dialog.showCertificateTrustDialog([browserWindow, ]options, callback)` _macOS_
 
-* `browserWindow` BrowserWindow
+* `browserWindow` BrowserWindow (optional)
 * `options` Object
   * `certificate` [Certificate](structures/certificate.md) - The certificate to trust/import.
   * `message` String - The message to display to the user.
@@ -186,6 +186,9 @@ and no GUI dialog will appear.
 Displays a modal dialog that shows a message and certificate information, and
 gives the user the option of trusting/importing the certificate.
 
+The `browserWindow` argument allows the dialog to attach itself to a parent
+window, making it modal.
+
 ## Sheets
 
 On macOS, dialogs are presented as sheets attached to a window if you provide

lib/browser/api/dialog.js

@@ -282,7 +282,9 @@ module.exports = {
     return binding.showErrorBox(...args)
   },
 
-  showCertificateTrustDialog: function (window, options, callback) {
+  showCertificateTrustDialog: function (...args) {
+    let [window, options, callback] = parseArgs(...args)
+
     if (options == null || typeof options !== 'object') {
       throw new TypeError('options must be an object')
     }