fix: folder open not working in devtools (#15396)

lib/renderer/inspector.js

@@ -2,10 +2,19 @@ window.onload = function () {
   // Use menu API to show context menu.
   window.InspectorFrontendHost.showContextMenuAtPoint = createMenu
 
+  // correct for Chromium returning undefined for filesystem
+  window.Persistence.FileSystemWorkspaceBinding.completeURL = completeURL
+
   // Use dialog API to override file chooser dialog.
   window.UI.createFileSelectorElement = createFileSelectorElement
 }
 
+// Extra / is needed as a result of MacOS requiring absolute paths
+function completeURL (project, path) {
+  project = 'file:///'
+  return `${project}${path}`
+}
+
 window.confirm = function (message, title) {
   const {dialog} = require('electron').remote
   if (title == null) {