(This is a merge of http://go/wvgerrit/134424.) This patch fixes code that would trigger -Wshorten-64-to-32 by implicitly narrowing a variable from 64 to 32 bits. The membarrier functions have their return type expanded so they can report the full return value of the syscall. Bug: 194971260 Test: x86-64 Change-Id: I5d948162b1f3f1540288df9494cabda39ecf8905