Fix broken test on Windows.

Has to be fixed with more internal hackery, unfortunately. Also, changed some
ASSERTs to RELEASE_ASSERTs in the page free / decommit / etc. routines. This
change would have prevented CQ success and the bad commit.

BUG=307705
TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/27485009

git-svn-id: svn://svn.chromium.org/blink/trunk@159875 bbb929c8-8fbe-4397-9dbb-9b2b20218538