From 5ba2e874b19c4de8be87644529747496519ac761 Mon Sep 17 00:00:00 2001
From: Hiroyuki Ikezoe <hikezoe@mozilla.com>
Date: Wed, 21 Feb 2018 19:33:59 +0900
Subject: [PATCH] Factor out a new function to check display property is
 changed from 'none' to other

---
 components/style/matching.rs              |  9 +--------
 components/style/properties/gecko.mako.rs | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/components/style/matching.rs b/components/style/matching.rs
index 89b60c9905a..82db5ded7ae 100644
--- a/components/style/matching.rs
+++ b/components/style/matching.rs
@@ -176,14 +176,7 @@ trait PrivateMatchMethods: TElement {
             return;
         }
 
-        let display_changed_from_none = old_values.map_or(false, |old| {
-            let old_display_style = old.get_box().clone_display();
-            let new_display_style = new_values.get_box().clone_display();
-            old_display_style == Display::None &&
-            new_display_style != Display::None
-        });
-
-        if display_changed_from_none {
+        if new_values.is_display_property_changed_from_none(old_values) {
             // When display value is changed from none to other, we need to
             // traverse descendant elements in a subsequent normal
             // traversal (we can't traverse them in this animation-only restyle
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 11b8ac5210a..aea141323ce 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -144,6 +144,22 @@ impl ComputedValues {
         return our_type == CSSPseudoElementType_InheritingAnonBox ||
                our_type == CSSPseudoElementType::NonInheritingAnonBox;
     }
+
+    /// Returns true if the display property is changed from 'none' to others.
+    pub fn is_display_property_changed_from_none(
+        &self,
+        old_values: Option<<&ComputedValues>
+    ) -> bool {
+        use properties::longhands::display::computed_value::T as Display;
+
+        old_values.map_or(false, |old| {
+            let old_display_style = old.get_box().clone_display();
+            let new_display_style = self.get_box().clone_display();
+            old_display_style == Display::None &&
+            new_display_style != Display::None
+        })
+    }
+
 }
 
 impl Drop for ComputedValues {