style: Make -moz-border-colors chrome only.

This also makes the `border` shorthand not reset them.

Bug: 1417200
Reviewed-by: xidorn
MozReview-Commit-ID: KNais1e5FnE

components/style/properties/longhand/border.mako.rs

@@ -74,6 +74,7 @@ ${helpers.gecko_keyword_conversion(Keyword('border-style',
                        spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-border-*-colors)"
                        products="gecko"
                        flags="APPLIES_TO_FIRST_LETTER"
+                       enabled_in="chrome"
                        ignored_when_colors_disabled="True">
         use std::fmt;
         use style_traits::ToCss;