Set FLAG_IMMUTABLE flag on FirstScreenBroadcast PendingIntent.

Fixing build by getting rid of the erroneously merged conflict markers,
and applying the end state of ag/14651125.

Bug: 183927137
Merged-In: I881a2b79462e8d420b3dcb6a6b98adbe9e8e0394
Change-Id: I70acd4ce48853be728be1fb80b4b885d00a059a9
1 file changed