Unify desktop Linux and Chrome OS font rendering params.

Unify desktop Linux and Chrome OS font rendering params.

Use the same path to get font rendering settings on desktop
Linux and Chrome OS: query the LinuxFontDelegate if it's set
and then query Fontconfig.

Also make the LinuxFontDelegate interface return a
PangoFontDescription directly (as opposed to an opaque
string that's actually a stringified PangoFontDescription)
and make it return a cached FontRenderParams struct instead
of exposing separate methods for looking up individual
properties.

Finally, add a missing build dependency on ui_test_pak, which
is needed to get the default font resource when running
gfx_unittests on Chrome OS.

BUG=125235,393067

Review URL: https://codereview.chromium.org/400193004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284255 0039d316-1c4b-4281-b951-d872f2087c98