Adrián Pérez de Castro authored Jun 06, 2017 and Michael Catanzaro committed Jun 30, 2017

This uses "font: menu" rules to pick the font configured to be used by GTK+
instead of hardcoding the "Cantarell" value.

Note that the CSS spec mandates that when "font: menu" is to be used, no
other properties (e.g. font size) can be specified as part of the "font"
attribute, and "font-size" attributes had to be added to change sizes.

This makes the following pages which are displayed by Epiphany inside
web views use the same font as the rest of GTK+:

  - New tab/window overview page.
  - Error pages.
  - about:
  - about:plugins
  - about:applications

Fixes bug #783489