From 3bd62cf0cd08ebaebd0298ed0560b759ffa95f05 Mon Sep 17 00:00:00 2001
From: enordin <enordin@mozilla.com>
Date: Tue, 3 Dec 2019 18:28:32 +0000
Subject: [PATCH] style: Check for border-image-* initial specified values when
 serializing border shorthand.

Differential Revision: https://phabricator.services.mozilla.com/D55588
---
 components/style/properties/shorthands/border.mako.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/components/style/properties/shorthands/border.mako.rs b/components/style/properties/shorthands/border.mako.rs
index c1bf200fe45..d584e568aed 100644
--- a/components/style/properties/shorthands/border.mako.rs
+++ b/components/style/properties/shorthands/border.mako.rs
@@ -179,6 +179,16 @@ pub fn parse_border<'i, 't>(
 
     impl<'a> ToCss for LonghandsToSerialize<'a>  {
         fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
+            use crate::properties::longhands;
+
+            // If any of the border-image longhands differ from their initial specified values we should not
+            // invoke serialize_directional_border(), so there is no point in continuing on to compute all_equal.
+            % for name in "outset repeat slice source width".split():
+                if *self.border_image_${name} != longhands::border_image_${name}::get_initial_specified_value() {
+                    return Ok(());
+                }
+            % endfor
+
             let all_equal = {
                 % for side in PHYSICAL_SIDES:
                   let border_${side}_width = self.border_${side}_width;