Auto merge of #17906 - emilio:calc-bgsize, r=hiro,birtles

style: Don't unconditionally generate Calc values when converting background-size from Gecko.

Bug: 1385140
MozReview-Commit-ID: ERwq50WSvLV

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components/style/gecko/conversions.rs

@@ -102,6 +102,16 @@ impl From<nsStyleCoord_CalcValue> for LengthOrPercentage {
     }
 }
 
+impl From<nsStyleCoord_CalcValue> for LengthOrPercentageOrAuto {
+    fn from(other: nsStyleCoord_CalcValue) -> LengthOrPercentageOrAuto {
+        match (other.mHasPercent, other.mLength) {
+            (false, _) => LengthOrPercentageOrAuto::Length(Au(other.mLength)),
+            (true, 0) => LengthOrPercentageOrAuto::Percentage(Percentage(other.mPercent)),
+            _ => LengthOrPercentageOrAuto::Calc(other.into()),
+        }
+    }
+}
+
 impl From<Angle> for CoordDataValue {
     fn from(reference: Angle) -> Self {
         match reference {

components/style/properties/gecko.mako.rs

@@ -3446,7 +3446,7 @@ fn static_assert() {
                 LengthOrPercentageOrAuto::Auto
             } else {
                 debug_assert!(ty == DimensionType::eLengthPercentage as u8);
-                LengthOrPercentageOrAuto::Calc(value.into())
+                value.into()
             }
         }