Make WallpaperMS bind wallpaper component PendingIntent immutable. am: b392903052 am: f75396d3c6 am: 286aa8b9b4 am: 7e53b78946

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12718696

Change-Id: I15107c6c6780c642467d8fa47c0a0b6f7dec95be