Make WallpaperMS bind wallpaper component PendingIntent immutable. am: b392903052 am: f75396d3c6 am: 286aa8b9b4 am: 7e53b78946 am: 7e24456d17 am: c201373d98

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

Change-Id: I648c5523d1895dd93a49e39431894d504ea74e2b