Fix reference to timezone variable - removed in VS 2015

It turns out that 'timezone' has been deprecated for a while. If
deprecation messages are enabled then VS 2013 says this when 'timezone'
is referenced:

warning C4996: 'timezone': This function or variable may be unsafe.
Consider using _get_timezone instead.

Sometimes features stay deprecated for decades, but in this case
'timezone' is now gone.

R=tsepez@chromium.org
BUG=440500

Review URL: https://codereview.chromium.org/1075673002
1 file changed