refactor: address TODO for WebContents type parsing (#18158)

lib/browser/chrome-extension.js

@@ -93,7 +93,7 @@ const startBackgroundPages = function (manifest) {
 
   const contents = webContents.create({
     partition: 'persist:__chrome_extension',
-    isBackgroundPage: true,
+    type: 'backgroundPage',
     sandbox: true,
     enableRemoteModule: false
   })

lib/browser/guest-view-manager.js

@@ -59,7 +59,7 @@ const createGuest = function (embedder, params) {
   }
 
   const guest = webContents.create({
-    isGuest: true,
+    type: 'webview',
     partition: params.partition,
     embedder: embedder
   })

lib/browser/guest-window-manager.js

@@ -28,7 +28,7 @@ const mergeOptions = function (child, parent, visited) {
 
   visited.add(parent)
   for (const key in parent) {
-    if (key === 'isBrowserView') continue
+    if (key === 'type') continue
     if (!hasProp.call(parent, key)) continue
     if (key in child && key !== 'webPreferences') continue
 
@@ -244,7 +244,7 @@ ipcMainInternal.on('ELECTRON_GUEST_WINDOW_MANAGER_INTERNAL_WINDOW_OPEN', functio
   options = mergeBrowserWindowOptions(event.sender, options)
   event.sender.emit('new-window', event, url, frameName, disposition, options, additionalFeatures, referrer)
   const { newGuest } = event
-  if ((event.sender.isGuest() && !event.sender.allowPopups) || event.defaultPrevented) {
+  if ((event.sender.getType() === 'webview' && !event.sender.allowPopups) || event.defaultPrevented) {
     if (newGuest != null) {
       if (options.webContents === newGuest.webContents) {
         // the webContents is not changed, so set defaultPrevented to false to