style: Add support for 'flex-basis:content' in the style system.

Bug: 1105111
Reviewed-by: xidorn
MozReview-Commit-ID: 5WhgHJJ0mDB

components/style/values/specified/flex.rs

@@ -8,22 +8,42 @@ use cssparser::Parser;
 use parser::{Parse, ParserContext};
 use style_traits::ParseError;
 use values::generics::flex::FlexBasis as GenericFlexBasis;
-use values::specified::length::LengthOrPercentage;
+
+/// The `width` value type.
+#[cfg(feature = "servo")]
+pub type Width = ::values::specified::NonNegativeLengthOrPercentageOrAuto;
+
+/// The `width` value type.
+#[cfg(feature = "gecko")]
+pub type Width = ::values::specified::MozLength;
 
 /// A specified value for the `flex-basis` property.
-pub type FlexBasis = GenericFlexBasis<LengthOrPercentage>;
+pub type FlexBasis = GenericFlexBasis<Width>;
 
 impl Parse for FlexBasis {
     fn parse<'i, 't>(
         context: &ParserContext,
-        input: &mut Parser<'i, 't>)
-    -> Result<Self, ParseError<'i>> {
-        if let Ok(length) = input.try(|i| LengthOrPercentage::parse_non_negative(context, i)) {
-            return Ok(GenericFlexBasis::Length(length));
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(width) = input.try(|i| Width::parse(context, i)) {
+            return Ok(GenericFlexBasis::Width(width));
         }
         try_match_ident_ignore_ascii_case! { input,
-            "auto" => Ok(GenericFlexBasis::Auto),
             "content" => Ok(GenericFlexBasis::Content),
         }
     }
 }
+
+impl FlexBasis {
+    /// `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        GenericFlexBasis::Width(Width::auto())
+    }
+
+    /// `0%`
+    #[inline]
+    pub fn zero_percent() -> Self {
+        GenericFlexBasis::Width(Width::zero_percent())
+    }
+}