Bug 1374233 - Part 7: Add NonNegativeLengthOrPercentage.

For padding-{*} and grid-{*}-gap.

MozReview-Commit-ID: 81G0b1k6JnD

components/style/values/specified/length.rs

@@ -1224,6 +1224,41 @@ impl Parse for LengthOrPercentageOrNone {
     }
 }
 
+/// A wrapper of LengthOrPercentage, whose value must be >= 0.
+pub type NonNegativeLengthOrPercentage = NonNegative<LengthOrPercentage>;
+
+impl From<NoCalcLength> for NonNegativeLengthOrPercentage {
+    #[inline]
+    fn from(len: NoCalcLength) -> Self {
+        NonNegative::<LengthOrPercentage>(LengthOrPercentage::from(len))
+    }
+}
+
+impl Parse for NonNegativeLengthOrPercentage {
+    #[inline]
+    fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
+        LengthOrPercentage::parse_non_negative(context, input).map(NonNegative::<LengthOrPercentage>)
+    }
+}
+
+impl NonNegativeLengthOrPercentage {
+    #[inline]
+    /// Returns a `zero` length.
+    pub fn zero() -> Self {
+        NonNegative::<LengthOrPercentage>(LengthOrPercentage::zero())
+    }
+
+    /// Parses a length or a percentage, allowing the unitless length quirk.
+    /// https://quirks.spec.whatwg.org/#the-unitless-length-quirk
+    #[inline]
+    pub fn parse_quirky<'i, 't>(context: &ParserContext,
+                                input: &mut Parser<'i, 't>,
+                                allow_quirks: AllowQuirks) -> Result<Self, ParseError<'i>> {
+        LengthOrPercentage::parse_non_negative_quirky(context, input, allow_quirks)
+            .map(NonNegative::<LengthOrPercentage>)
+    }
+}
+
 /// Either a `<length>` or the `none` keyword.
 pub type LengthOrNone = Either<Length, None_>;