[automerger skipped] [DO NOT MERGE] Make GlobalScreenshot PendingIntents immutable am: f4eefc55c4 am: 4cccd0c4e3 -s ours am: 67bd3caef0 am: 2170554e98 am: bff57c4da0

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12773073

Change-Id: Ieb30fe9a56e9bffe458697df44f6432d5c8becf7