Merge "Mark implicit PendingIntents as immutable" into rvc-dev am: e35ad478dc am: 205fd265d0 am: 0288878d81

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12296407

Change-Id: I69bd76af5a2912c23ba9ec53fce7a7540fba0542