Method does as advertised using select() on POSIX and the existing
CancelableFileOperation() wrapper on Windows since there is no
select() equivalent on XP.
It was also high time we had some unit tests for this class, so I
added a small set which exercise almost the full functionality.
BUG=289124
TEST=base_unittests!
Review URL: https://codereview.chromium.org/23875019
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229621 0039d316-1c4b-4281-b951-d872f2087c98
