ASLR is much weaker in a 2GB address space. Plus the vast
majority of 32-bit Windows hosts are XP, which don't have
ASLR anyway. So, avoid the fragmentation and skip it in
this case.

BUG=chromium:394591
LOG=Y
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/1385023002

Cr-Commit-Position: refs/heads/master@{#31127}