style: Implement flow-relative values for resize property.

Differential Revision: https://phabricator.services.mozilla.com/D2908

components/style/properties/data.py

@@ -325,6 +325,7 @@ class Longhand(object):
                 "OverflowClipBox",
                 "OverscrollBehavior",
                 "Percentage",
+                "Resize",
                 "SVGOpacity",
                 "SVGPaintOrder",
                 "ScrollSnapType",

components/style/properties/gecko.mako.rs

@@ -3106,6 +3106,9 @@ fn static_assert() {
     ) %>
     ${impl_keyword('clear', 'mBreakType', clear_keyword)}
 
+    <% resize_keyword = Keyword("resize", "None Both Horizontal Vertical") %>
+    ${impl_keyword('resize', 'mResize', resize_keyword)}
+
     <% overflow_x = data.longhands_by_name["overflow-x"] %>
     pub fn set_overflow_y(&mut self, v: longhands::overflow_y::computed_value::T) {
         use properties::longhands::overflow_x::computed_value::T as BaseType;

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

@@ -422,17 +422,21 @@ ${helpers.single_keyword("page-break-inside",
 
 // CSS Basic User Interface Module Level 3
 // http://dev.w3.org/csswg/css-ui
-// FIXME support logical values `block` and `inline` (https://drafts.csswg.org/css-logical-props/#resize)
 //
 // This is APPLIES_TO_PLACEHOLDER so we can override, in the UA sheet, the
 // 'resize' property we'd inherit from textarea otherwise.  Basically, just
 // makes the UA rules easier to write.
-${helpers.single_keyword("resize",
-                         "none both horizontal vertical",
-                         products="gecko",
-                         spec="https://drafts.csswg.org/css-ui/#propdef-resize",
-                         flags="APPLIES_TO_PLACEHOLDER",
-                         animation_value_type="discrete")}
+${helpers.predefined_type(
+    "resize",
+    "Resize",
+    "computed::Resize::None",
+    products="gecko",
+    animation_value_type="discrete",
+    needs_context=False,
+    gecko_ffi_name="mResize",
+    flags="APPLIES_TO_PLACEHOLDER",
+    spec="https://drafts.csswg.org/css-ui/#propdef-resize",
+)}
 
 ${helpers.predefined_type(
     "perspective",