style: Remove old CSS scroll snap implementation.

This will save us some time from figuring out what's the best thing to do in
bug 1552587, so that other patches I have in flight (mainly bug 1552708) can
land, since we cannot add a single byte to nsStyleDisplay right now otherwise.

The code removed here is well isolated and not that complicated, so it seems to
me that should be easy to bring back should we have an emergency (and I commit
to doing that while preserving the nsStyleDisplay size limit if we need to :)).

Differential Revision: https://phabricator.services.mozilla.com/D32026

components/style/properties/gecko.mako.rs

@@ -696,28 +696,6 @@ def set_gecko_property(ffi_name, expr):
     }
 </%def>
 
-<%def name="impl_style_coord(ident, gecko_ffi_name)">
-    #[allow(non_snake_case)]
-    pub fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
-        v.to_gecko_style_coord(&mut self.gecko.${gecko_ffi_name});
-    }
-    #[allow(non_snake_case)]
-    pub fn copy_${ident}_from(&mut self, other: &Self) {
-        self.gecko.${gecko_ffi_name}.copy_from(&other.gecko.${gecko_ffi_name});
-    }
-    #[allow(non_snake_case)]
-    pub fn reset_${ident}(&mut self, other: &Self) {
-        self.copy_${ident}_from(other)
-    }
-
-    #[allow(non_snake_case)]
-    pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
-        use crate::properties::longhands::${ident}::computed_value::T;
-        T::from_gecko_style_coord(&self.gecko.${gecko_ffi_name})
-            .expect("clone for ${ident} failed")
-    }
-</%def>
-
 <%def name="copy_sides_style_coord(ident)">
     <% gecko_ffi_name = "m" + to_camel_case(ident) %>
     #[allow(non_snake_case)]
@@ -2184,9 +2162,8 @@ fn static_assert() {
                           animation-iteration-count animation-timing-function
                           clear transition-duration transition-delay
                           transition-timing-function transition-property
-                          transform-style scroll-snap-points-x
-                          scroll-snap-points-y scroll-snap-coordinate
-                          -moz-binding shape-outside -webkit-line-clamp""" %>
+                          transform-style -moz-binding shape-outside
+                          -webkit-line-clamp""" %>
 <%self:impl_trait style_struct_name="Box" skip_longhands="${skip_box_longhands}">
     #[inline]
     pub fn set_display(&mut self, v: longhands::display::computed_value::T) {
@@ -2226,33 +2203,7 @@ fn static_assert() {
         gecko_inexhaustive=True,
     ) %>
     ${impl_keyword('clear', 'mBreakType', clear_keyword)}
-
-    ${impl_style_coord("scroll_snap_points_x", "mScrollSnapPointsX")}
-    ${impl_style_coord("scroll_snap_points_y", "mScrollSnapPointsY")}
-
-    pub fn set_scroll_snap_coordinate<I>(&mut self, v: I)
-        where I: IntoIterator<Item = longhands::scroll_snap_coordinate::computed_value::single_value::T>,
-              I::IntoIter: ExactSizeIterator
-    {
-        self.gecko.mScrollSnapCoordinate.assign_from_iter_pod(v.into_iter());
-    }
-
-    pub fn copy_scroll_snap_coordinate_from(&mut self, other: &Self) {
-        let iter = other.gecko.mScrollSnapCoordinate.iter().map(|c| *c);
-        self.gecko.mScrollSnapCoordinate.assign_from_iter_pod(iter);
-    }
-
-    pub fn reset_scroll_snap_coordinate(&mut self, other: &Self) {
-        self.copy_scroll_snap_coordinate_from(other)
-    }
-
-    pub fn clone_scroll_snap_coordinate(&self) -> longhands::scroll_snap_coordinate::computed_value::T {
-        let vec = self.gecko.mScrollSnapCoordinate.iter().cloned().collect();
-        longhands::scroll_snap_coordinate::computed_value::List(vec)
-    }
-
     ${impl_css_url('_moz_binding', 'mBinding')}
-
     ${impl_transition_time_value('delay', 'Delay')}
     ${impl_transition_time_value('duration', 'Duration')}
     ${impl_transition_timing_function()}

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

@@ -309,41 +309,6 @@ ${helpers.predefined_type(
     allowed_in_keyframe_block=False,
 )}
 
-% for axis in ["x", "y"]:
-    ${helpers.predefined_type(
-        "scroll-snap-points-" + axis,
-        "ScrollSnapPoint",
-        "computed::ScrollSnapPoint::none()",
-        animation_value_type="discrete",
-        gecko_pref="layout.css.scroll-snap.enabled",
-        products="gecko",
-        spec="Nonstandard (https://www.w3.org/TR/2015/WD-css-snappoints-1-20150326/#scroll-snap-points)",
-    )}
-% endfor
-
-${helpers.predefined_type(
-    "scroll-snap-destination",
-    "Position",
-    "computed::Position::zero()",
-    products="gecko",
-    gecko_pref="layout.css.scroll-snap.enabled",
-    boxed=True,
-    spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/scroll-snap-destination)",
-    animation_value_type="discrete",
-)}
-
-${helpers.predefined_type(
-    "scroll-snap-coordinate",
-    "Position",
-    "computed::Position::zero()",
-    vector=True,
-    allow_empty=True,
-    products="gecko",
-    gecko_pref="layout.css.scroll-snap.enabled",
-    spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/scroll-snap-destination)",
-    animation_value_type="discrete",
-)}
-
 <% transform_extra_prefixes = "moz:layout.css.prefixes.transforms webkit" %>
 
 ${helpers.predefined_type(