Auto merge of #17251 - chenpighead:stylo-stop-flood-opacity-animatabl…

…e, r=hiro

stylo: make {stop, flood}-opacity animatable

This is just the servo part change. The test part will be landed in gecko directly.

Gecko bug: [Bug 1360133](https://bugzilla.mozilla.org/show_bug.cgi?id=1360133)

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

@@ -28,7 +28,7 @@ ${helpers.predefined_type(
 
 ${helpers.predefined_type("stop-opacity", "Opacity", "1.0",
                           products="gecko",
-                          animation_value_type="none",
+                          animation_value_type="ComputedValue",
                           spec="https://www.w3.org/TR/SVGTiny12/painting.html#propdef-stop-opacity")}
 
 // Section 15 - Filter Effects
@@ -41,7 +41,7 @@ ${helpers.predefined_type(
     spec="https://www.w3.org/TR/SVG/filters.html#FloodColorProperty")}
 
 ${helpers.predefined_type("flood-opacity", "Opacity",
-                          "1.0", products="gecko", animation_value_type="none",
+                          "1.0", products="gecko", animation_value_type="ComputedValue",
                           spec="https://www.w3.org/TR/SVG/filters.html#FloodOpacityProperty")}
 
 ${helpers.predefined_type(