Enable webview in sandbox renderer (#13435)

* Enable webview in sandbox renderer
Security: Inherit embedder prefs onto webview

* cache lastwebprefs

lib/browser/guest-view-manager.js

@@ -240,6 +240,23 @@ const attachGuest = function (event, elementInstanceId, guestInstanceId, params)
     webPreferences.disablePopups = true
   }
 
+  // Security options that guest will always inherit from embedder
+  const inheritedWebPreferences = new Map([
+    ['contextIsolation', true],
+    ['javascript', false],
+    ['nativeWindowOpen', true],
+    ['nodeIntegration', false],
+    ['sandbox', true]
+  ])
+
+  // Inherit certain option values from embedder
+  const lastWebPreferences = embedder.getLastWebPreferences()
+  for (const [name, value] of inheritedWebPreferences) {
+    if (lastWebPreferences[name] === value) {
+      webPreferences[name] = value
+    }
+  }
+
   embedder.emit('will-attach-webview', event, webPreferences, params)
   if (event.defaultPrevented) {
     if (guest.viewInstanceId == null) guest.viewInstanceId = params.instanceId