style: Add SVG geometry property support in CSS.

This patch adds SVG geometry properties to CSS, it doesn't deal with
how SVG handles them.

Differential Revision: https://phabricator.services.mozilla.com/D29937

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

@@ -191,3 +191,66 @@ ${helpers.predefined_type(
     animation_value_type="discrete",
     flags="CREATES_STACKING_CONTEXT",
 )}
+
+${helpers.predefined_type(
+    "x",
+    "LengthPercentage",
+    "computed::LengthPercentage::zero()",
+    products="gecko",
+    animation_value_type="ComputedValue",
+    spec="https://svgwg.org/svg2-draft/geometry.html#X",
+)}
+
+${helpers.predefined_type(
+    "y",
+    "LengthPercentage",
+    "computed::LengthPercentage::zero()",
+    products="gecko",
+    animation_value_type="ComputedValue",
+    spec="https://svgwg.org/svg2-draft/geometry.html#Y",
+)}
+
+${helpers.predefined_type(
+    "cx",
+    "LengthPercentage",
+    "computed::LengthPercentage::zero()",
+    products="gecko",
+    animation_value_type="ComputedValue",
+    spec="https://svgwg.org/svg2-draft/geometry.html#CX",
+)}
+
+${helpers.predefined_type(
+    "cy",
+    "LengthPercentage",
+    "computed::LengthPercentage::zero()",
+    products="gecko",
+    animation_value_type="ComputedValue",
+    spec="https://svgwg.org/svg2-draft/geometry.html#CY",
+)}
+
+${helpers.predefined_type(
+    "rx",
+    "NonNegativeLengthPercentageOrAuto",
+    "computed::NonNegativeLengthPercentageOrAuto::auto()",
+    products="gecko",
+    animation_value_type="LengthPercentageOrAuto",
+    spec="https://svgwg.org/svg2-draft/geometry.html#RX",
+)}
+
+${helpers.predefined_type(
+    "ry",
+    "NonNegativeLengthPercentageOrAuto",
+    "computed::NonNegativeLengthPercentageOrAuto::auto()",
+    products="gecko",
+    animation_value_type="LengthPercentageOrAuto",
+    spec="https://svgwg.org/svg2-draft/geometry.html#RY",
+)}
+
+${helpers.predefined_type(
+    "r",
+    "NonNegativeLengthPercentage",
+    "computed::NonNegativeLengthPercentage::zero()",
+    products="gecko",
+    animation_value_type="LengthPercentage",
+    spec="https://svgwg.org/svg2-draft/geometry.html#R",
+)}