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

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

Change-Id: I477fd6157285c642fde521428d5a9d4ac43bcebc