patch.diff

diff --git a/gfx/webrender/src/display_list_flattener.rs b/gfx/webrender/src/display_list_flattener.rs
index 525e79e837e2..3498892e1139 100644
--- a/gfx/webrender/src/display_list_flattener.rs
+++ b/gfx/webrender/src/display_list_flattener.rs
@@ -1029,6 +1029,15 @@ impl<'a> DisplayListFlattener<'a> {
             None
         };
 
+        let mut ancestor_is_backface_visible = is_backface_visible;
+        for sc in self.sc_stack.iter().rev() {
+            if sc.transform_style == TransformStyle::Flat {
+                ancestor_is_backface_visible = sc.is_backface_visible;
+                break;
+            }
+        }
+
+
         let mut parent_prim_index = if !establishes_3d_context && participating_in_3d_context {
             // If we're in a 3D context, we will parent the picture
             // to the first stacking context we find that is a
@@ -1162,6 +1171,8 @@ impl<'a> DisplayListFlattener<'a> {
         // Add this as the top-most picture for primitives to be added to.
         self.picture_stack.push(sc_prim_index);
 
+        let is_backface_visible = is_backface_visible && ancestor_is_backface_visible;
+
         // Push the SC onto the stack, so we know how to handle things in
         // pop_stacking_context.
         let sc = FlattenedStackingContext {