style: Make flex-flow serialization interoperable

Differential Revision: https://phabricator.services.mozilla.com/D180270

1 files changed, 15 insertions, 1 deletions

diff --git a/components/style/properties/shorthands/position.mako.rs b/components/style/properties/shorthands/position.mako.rs
index 471e67c0986..6d2b47d345f 100644
--- a/components/style/properties/shorthands/position.mako.rs
+++ b/components/style/properties/shorthands/position.mako.rs
@@ -9,7 +9,6 @@
                     servo_pref="layout.flexbox.enabled",
                     sub_properties="flex-direction flex-wrap"
                     extra_prefixes="webkit"
-                    derive_serialize="True"
                     spec="https://drafts.csswg.org/css-flexbox/#flex-flow-property">
     use crate::properties::longhands::{flex_direction, flex_wrap};
 
@@ -43,6 +42,21 @@
             flex_wrap: unwrap_or_initial!(flex_wrap, wrap),
         })
     }
+
+    impl<'a> ToCss for LonghandsToSerialize<'a> {
+        fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
+            if *self.flex_direction == flex_direction::get_initial_specified_value() &&
+               *self.flex_wrap != flex_wrap::get_initial_specified_value() {
+                return self.flex_wrap.to_css(dest)
+            }
+            self.flex_direction.to_css(dest)?;
+            if *self.flex_wrap != flex_wrap::get_initial_specified_value() {
+                dest.write_char(' ')?;
+                self.flex_wrap.to_css(dest)?;
+            }
+            Ok(())
+        }
+    }
 </%helpers:shorthand>
 
 <%helpers:shorthand name="flex"