From 1346be59b26fd23e3afe735e48c81b5e1e973130 Mon Sep 17 00:00:00 2001
From: Cameron McCormack <cam@mcc.id.au>
Date: Wed, 13 Sep 2017 16:06:48 +0800
Subject: [PATCH] style: Add writing mode dependency if special MozLength
 keywords are used.

---
 components/style/values/computed/length.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/components/style/values/computed/length.rs b/components/style/values/computed/length.rs
index a83e86bd1e6..96754018f9f 100644
--- a/components/style/values/computed/length.rs
+++ b/components/style/values/computed/length.rs
@@ -862,6 +862,10 @@ impl ToComputedValue for specified::MozLength {
                 MozLength::LengthOrPercentageOrAuto(lopoa.to_computed_value(context))
             }
             specified::MozLength::ExtremumLength(ref ext) => {
+                debug_assert!(context.for_non_inherited_property.is_some(),
+                              "should check whether we're a non-inherited property");
+                context.rule_cache_conditions.borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
                 MozLength::ExtremumLength(ext.clone())
             }
         }