Protect GrantCredentialsPermissionActivity against overlay. am: f45dcfe1f5 am: 3f47c701f1 am: 765788de9a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/13029378

Change-Id: I109082c688a79e2d4a94277d2eab4dd7b8f9747e