fix: manually manage WebContents of webview when it is detached

lib/renderer/web-view/guest-view-internal.js

@@ -94,6 +94,9 @@ module.exports = {
   createGuestSync: function (params) {
     return ipcRenderer.sendSync('ELECTRON_GUEST_VIEW_MANAGER_CREATE_GUEST_SYNC', params)
   },
+  destroyGuest: function (guestInstanceId) {
+    ipcRenderer.send('ELECTRON_GUEST_VIEW_MANAGER_DESTROY_GUEST', guestInstanceId)
+  },
   attachGuest: function (elementInstanceId, guestInstanceId, params, contentWindow) {
     const embedderFrameId = webFrame.getWebFrameId(contentWindow)
     if (embedderFrameId < 0) {  // this error should not happen.

lib/renderer/web-view/web-view.js

@@ -76,6 +76,7 @@ class WebViewImpl {
     // heard back from createGuest yet. We will not reset the flag in this case so
     // that we don't end up allocating a second guest.
     if (this.guestInstanceId) {
+      guestViewInternal.destroyGuest(this.guestInstanceId)
       this.guestInstanceId = void 0
     }