Merge "simpleperf: check invalid pid in ForkThread()." am: 1e427d7d5d

Original change: https://android-review.googlesource.com/c/platform/system/extras/+/2356863

Change-Id: I394d07438eceeed6e1cd5056551227c971fa9234
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>