Fix failing tests on Debian Wheezy

Some PrintLayoutTests failed on Wheezy because of rounding
differences related to font metrics. This change modifies the
dpi values we use for the PrintLayoutTests to make the tests
more platform independent. It uses internal knowledge of the
TimesNewRoman font to calculate a dpi value that minimizes rounding
problems.

Change-Id: I403de5ad724d44438597c33c16326c1989f31939