Merge "Mark implicit PendingIntents as immutable am: 599c3e4b75 am: fa64ffd0a2 am: 3ff2a5cbd1 am: 6cb8e4a157 am: 31d1d2162e" into rvc-qpr-dev-plus-aosp am: 712addd559

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12296405

Change-Id: I97c51786eede69464cf6c530c5ffd0503e9be0af