Add base::mac::ScopedMachVM::reset_unaligned()

In certain circumstances, like managing regions of memory sent over Mach
IPC as OOL memory, the address/size may not be a multiple of PAGE_SIZE.

This also adds a test for ScopedMachVM.

Bug: 932175
Change-Id: I9c48534fefd8c66122d74ff7ed0b78a719cc0fad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1532745
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643042}
4 files changed