Bug 1613624 - Make it possible to disable system fonts in wpt, r=maja_zf

wpt previously required Ahem as a system font. That requirement is now
relaxed and installing fonts is only required in order to see bugs
that result from differences between the system font loader and the
webfont loader. Since installing fonts can cause problems on some
systems, make this possible to disable.

Differential Revision: https://phabricator.services.mozilla.com/D61801

--HG--
extra : moz-landing-system : lando

testing/web-platform/mach_commands.py

@@ -101,11 +101,13 @@ class WebPlatformTestsRunnerSetup(MozbuildObject):
             kwargs["webdriver_binary"] = self.get_binary_path("geckodriver", validate_exists=False)
 
 
-        if mozinfo.info["os"] == "win" and mozinfo.info["os_version"] == "6.1":
+        if kwargs["install_fonts"] is None:
+            kwargs["install_fonts"] = True
+
+        if kwargs["install_fonts"] and mozinfo.info["os"] == "win" and mozinfo.info["os_version"] == "6.1":
             # On Windows 7 --install-fonts fails, so fall back to a Firefox-specific codepath
             self.setup_fonts_firefox()
-        else:
-            kwargs["install_fonts"] = True
+            kwargs["install_fonts"] = False
 
         kwargs = wptcommandline.check_args(kwargs)
 

testing/web-platform/tests/tools/wptrunner/wptrunner/wptcommandline.py

@@ -210,7 +210,9 @@ scheme host and port.""")
                               help="Path to config file")
     config_group.add_argument("--install-fonts", action="store_true",
                               default=None,
-                              help="Allow the wptrunner to install fonts on your system")
+                              help="Install additional system fonts on your system")
+    config_group.add_argument("--no-install-fonts", dest="install_fonts", action="store_false",
+                              help="Do not install additional system fonts on your system")
     config_group.add_argument("--font-dir", action="store", type=abs_path, dest="font_dir",
                               help="Path to local font installation directory", default=None)
     config_group.add_argument("--headless", action="store_true",