From 1c48a3bedb8b08b264279965b7c408cb24ab183d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Naz=C4=B1m=20Can=20Alt=C4=B1nova?= <canaltinova@gmail.com>
Date: Tue, 5 Dec 2017 22:58:48 +0300
Subject: [PATCH] stylo: Hide accidentally exposed subgrid behind prefs

---
 components/style/values/specified/grid.rs | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/components/style/values/specified/grid.rs b/components/style/values/specified/grid.rs
index f2b8453c46c..8c4d7d225d8 100644
--- a/components/style/values/specified/grid.rs
+++ b/components/style/values/specified/grid.rs
@@ -326,6 +326,19 @@ impl ToComputedValue for TrackList<LengthOrPercentage, Integer> {
     }
 }
 
+#[cfg(feature = "gecko")]
+#[inline]
+fn allow_grid_template_subgrids() -> bool {
+    use gecko_bindings::structs::mozilla;
+    unsafe { mozilla::StylePrefs_sGridTemplateSubgridValueEnabled }
+}
+
+#[cfg(feature = "servo")]
+#[inline]
+fn allow_grid_template_subgrids() -> bool {
+    false
+}
+
 impl Parse for GridTemplateComponent<LengthOrPercentage, Integer> {
     // FIXME: Derive Parse (probably with None_)
     fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
@@ -343,10 +356,12 @@ impl GridTemplateComponent<LengthOrPercentage, Integer> {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        if let Ok(t) = input.try(|i| TrackList::parse(context, i)) {
-            return Ok(GridTemplateComponent::TrackList(t))
+        if allow_grid_template_subgrids() {
+            if let Ok(t) = input.try(|i| LineNameList::parse(context, i)) {
+                return Ok(GridTemplateComponent::Subgrid(t))
+            }
         }
 
-        LineNameList::parse(context, input).map(GridTemplateComponent::Subgrid)
+        TrackList::parse(context, input).map(GridTemplateComponent::TrackList)
     }
 }