[automerger skipped] [DO NOT MERGE] Make GlobalScreenshot PendingIntents immutable am: 44124798 am: 40297a24 am: 368eecbe -s ours am: b20d5c3a -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12773217

Change-Id: I0a3aa91d8ac192c840917dfb218ebdb79c72bc9b