Auto merge of #16754 - canaltinova:text-shadow, r=emilio

Fix parsing behavior of text-shadow property

Blur radius should reject negative values. There was already `Shadow` struct for properties like this. `filter: drop-shadow` also has the same syntax with that property. I thought sharing the same code would be better and used Shadow struct for parsing. Converted to SpecifiedTextShadow to get rid of unneccessary fields and to be able to convert its computed value. Maybe it would be better to avoid using `Shadow` or just using `Shadow` but sharing code and avoiding unneccessary fields seems better.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

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

@@ -720,12 +720,13 @@ ${helpers.single_keyword("text-align-last",
     use cssparser;
     use std::fmt;
     use style_traits::ToCss;
+    use values::specified::Shadow;
     use values::HasViewportPercentage;
 
     impl HasViewportPercentage for SpecifiedValue {
         fn has_viewport_percentage(&self) -> bool {
             let &SpecifiedValue(ref vec) = self;
-            vec.iter().any(|ref x| x .has_viewport_percentage())
+            vec.iter().any(|ref x| x.has_viewport_percentage())
         }
     }
 
@@ -750,6 +751,17 @@ ${helpers.single_keyword("text-align-last",
         pub color: Option<specified::CSSColor>,
     }
 
+    impl From<Shadow> for SpecifiedTextShadow {
+        fn from(shadow: Shadow) -> SpecifiedTextShadow {
+            SpecifiedTextShadow {
+                offset_x: shadow.offset_x,
+                offset_y: shadow.offset_y,
+                blur_radius: shadow.blur_radius,
+                color: shadow.color,
+            }
+        }
+    }
+
     pub mod computed_value {
         use app_units::Au;
         use cssparser::Color;
@@ -772,15 +784,13 @@ ${helpers.single_keyword("text-align-last",
     impl ToCss for computed_value::T {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
             let mut iter = self.0.iter();
-            if let Some(shadow) = iter.next() {
+            match iter.next() {
-                try!(shadow.to_css(dest));
+                Some(shadow) => shadow.to_css(dest)?,
-            } else {
+                None => return dest.write_str("none"),
-                try!(dest.write_str("none"));
-                return Ok(())
             }
             for shadow in iter {
-                try!(dest.write_str(", "));
+                dest.write_str(", ")?;
-                try!(shadow.to_css(dest));
+                shadow.to_css(dest)?;
             }
             Ok(())
         }
@@ -788,29 +798,26 @@ ${helpers.single_keyword("text-align-last",
 
     impl ToCss for computed_value::TextShadow {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-            try!(self.offset_x.to_css(dest));
+            self.offset_x.to_css(dest)?;
-            try!(dest.write_str(" "));
+            dest.write_str(" ")?;
-            try!(self.offset_y.to_css(dest));
+            self.offset_y.to_css(dest)?;
-            try!(dest.write_str(" "));
+            dest.write_str(" ")?;
-            try!(self.blur_radius.to_css(dest));
+            self.blur_radius.to_css(dest)?;
-            try!(dest.write_str(" "));
+            dest.write_str(" ")?;
-            try!(self.color.to_css(dest));
+            self.color.to_css(dest)
-            Ok(())
         }
     }
 
     impl ToCss for SpecifiedValue {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
             let mut iter = self.0.iter();
-            if let Some(shadow) = iter.next() {
+            match iter.next() {
-                try!(shadow.to_css(dest));
+                Some(shadow) => shadow.to_css(dest)?,
-            } else {
+                None => return dest.write_str("none"),
-                try!(dest.write_str("none"));
-                return Ok(())
             }
             for shadow in iter {
-                try!(dest.write_str(", "));
+                dest.write_str(", ")?;
-                try!(shadow.to_css(dest));
+                shadow.to_css(dest)?;
             }
             Ok(())
         }
@@ -818,15 +825,15 @@ ${helpers.single_keyword("text-align-last",
 
     impl ToCss for SpecifiedTextShadow {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-            try!(self.offset_x.to_css(dest));
+            self.offset_x.to_css(dest)?;
-            try!(dest.write_str(" "));
+            dest.write_str(" ")?;
-            try!(self.offset_y.to_css(dest));
+            self.offset_y.to_css(dest)?;
-            try!(dest.write_str(" "));
+            dest.write_str(" ")?;
-            try!(self.blur_radius.to_css(dest));
+            self.blur_radius.to_css(dest)?;
 
             if let Some(ref color) = self.color {
-                try!(dest.write_str(" "));
+                dest.write_str(" ")?;
-                try!(color.to_css(dest));
+                color.to_css(dest)?;
             }
             Ok(())
         }
@@ -842,61 +849,12 @@ ${helpers.single_keyword("text-align-last",
         if input.try(|input| input.expect_ident_matching("none")).is_ok() {
             Ok(SpecifiedValue(Vec::new()))
         } else {
-            input.parse_comma_separated(|i| parse_one_text_shadow(context, i)).map(SpecifiedValue)
+            input.parse_comma_separated(|i| {
+                Ok(SpecifiedTextShadow::from(Shadow::parse(context, i, true)?))
+            }).map(SpecifiedValue)
         }
     }
 
-    fn parse_one_text_shadow(context: &ParserContext, input: &mut Parser) -> Result<SpecifiedTextShadow,()> {
-        use app_units::Au;
-        let mut lengths = [specified::Length::zero(), specified::Length::zero(), specified::Length::zero()];
-        let mut lengths_parsed = false;
-        let mut color = None;
-
-        loop {
-            if !lengths_parsed {
-                if let Ok(value) = input.try(|i| specified::Length::parse(context, i)) {
-                    lengths[0] = value;
-                    let mut length_parsed_count = 1;
-                    while length_parsed_count < 3 {
-                        if let Ok(value) = input.try(|i| specified::Length::parse(context, i)) {
-                            lengths[length_parsed_count] = value
-                        } else {
-                            break
-                        }
-                        length_parsed_count += 1;
-                    }
-
-                    // The first two lengths must be specified.
-                    if length_parsed_count < 2 {
-                        return Err(())
-                    }
-
-                    lengths_parsed = true;
-                    continue
-                }
-            }
-            if color.is_none() {
-                if let Ok(value) = input.try(|i| specified::CSSColor::parse(context, i)) {
-                    color = Some(value);
-                    continue
-                }
-            }
-            break
-        }
-
-        // Lengths must be specified.
-        if !lengths_parsed {
-            return Err(())
-        }
-
-        Ok(SpecifiedTextShadow {
-            offset_x: lengths[0].take(),
-            offset_y: lengths[1].take(),
-            blur_radius: lengths[2].take(),
-            color: color,
-        })
-    }
-
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;