layout: Implement pointer-events: none per SVG 1.1 § 16.6.

SVG-only values are not yet supported.

components/style/properties/mod.rs.mako

@@ -1543,6 +1543,11 @@ pub mod longhands {
         }
     </%self:single_component_value>
 
+    // NB: `pointer-events: auto` (and use of `pointer-events` in anything that isn't SVG, in fact)
+    // is nonstandard, slated for CSS4-UI.
+    // TODO(pcwalton): SVG-only values.
+    ${single_keyword("pointer-events", "auto none")}
+
     // Box-shadow, etc.
     ${new_style_struct("Effects", is_inherited=False)}