Merge "Add FLAG_IMMUTABLE to PendingIntents" am: a3aa817aa5

Original change: https://android-review.googlesource.com/c/platform/development/+/2229375

Change-Id: I922df5e7b14e99bc925e77f33acfd6abeb0785a0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>