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

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

Change-Id: I94c6829b8db0c9b212c111c8b70ab7e3d91ba4bc