Add base_unittests to win8 trybot. Fix PEImage tests.
Two fixes were required to work on win8:
1. To determine if a directory is a reparse point, use GetFileInformation() since using WIN32_FIND_DATA.dwFileAttributes doesn't work on Windows 8. See https://msdn.microsoft.com/en-us/library/windows/desktop/aa363940.aspx
2. Update the PE image tests to use its own binary, change the expectation format, add support for Win 8.1 and re-enable on 64-bit.
BUG=373973,167707
Review URL: https://codereview.chromium.org/946183002
Cr-Commit-Position: refs/heads/master@{#317960}
7 files changed
