Merge "libbinder: remove unused 'pool' var" am: 226376f9f6 am: 24eb9449e9 am: 1f08aa3f58

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/1702011

Change-Id: I666e525d117ea78be9c84303dc3a3ba707f9c19d