Uncomment more stuff related to box construction

components/style/properties/longhands/box.mako.rs

@@ -42,15 +42,24 @@ ${helpers.single_keyword(
     spec="Internal (not web-exposed)",
 )}
 
-${helpers.single_keyword(
-    "position",
-    "static absolute relative fixed" + (" sticky" if engine in ["gecko", "servo-2013"] else ""),
-    engines="gecko servo-2013 servo-2020",
-    animation_value_type="discrete",
-    flags="CREATES_STACKING_CONTEXT ABSPOS_CB",
-    spec="https://drafts.csswg.org/css-position/#position-property",
-    servo_restyle_damage="rebuild_and_reflow",
-)}
+<%helpers:single_keyword
+    name="position"
+    values="static absolute relative fixed ${'sticky' if engine in ['gecko', 'servo-2013'] else ''}"
+    engines="gecko servo-2013 servo-2020"
+    animation_value_type="discrete"
+    flags="CREATES_STACKING_CONTEXT ABSPOS_CB"
+    spec="https://drafts.csswg.org/css-position/#position-property"
+    servo_restyle_damage="rebuild_and_reflow"
+>
+impl computed_value::T {
+    pub fn is_absolutely_positioned(self) -> bool {
+        match self {
+            Self::Absolute | Self::Fixed => true,
+            _ => false,
+        }
+    }
+}
+</%helpers:single_keyword>
 
 ${helpers.predefined_type(
     "float",

components/style/values/computed/box.rs

@@ -61,6 +61,13 @@ pub enum Float {
     None,
 }
 
+impl Float {
+    /// Returns true if `self` is not `None`.
+    pub fn is_floating(self) -> bool {
+        self != Self::None
+    }
+}
+
 impl ToComputedValue for SpecifiedFloat {
     type ComputedValue = Float;