Make SyzyAsan support the allocation > 1GB

Currently SyzyAsan doesn't support the allocations > 1GB (although we don't enforce this, see crbug.com/656554). This is causing an issue when using it on a Large Address Aware applications because this kind of allocations are valid.

This also make the SyzyAsan tests run in 4G mode by default.

BUG=656554
R=chrisha@chromium.org

Review URL: https://codereview.chromium.org/2527533003 .
7 files changed