Change ToCss to take a CssWriter<W>

This more concrete wrapper type can write a prefix the very first time something
is written to it. This allows removing plenty of useless monomorphisations caused
by the former W/SequenceWriter<W> pair of types.

1 files changed, 6 insertions, 3 deletions

diff --git a/components/style/values/computed/position.rs b/components/style/values/computed/position.rs
index ed6a308151f..abd3522382d 100644
--- a/components/style/values/computed/position.rs
+++ b/components/style/values/computed/position.rs
@@ -7,8 +7,8 @@
 //!
 //! [position]: https://drafts.csswg.org/css-backgrounds-3/#position
 
-use std::fmt;
-use style_traits::ToCss;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
 use values::computed::{LengthOrPercentage, Percentage};
 use values::generics::position::Position as GenericPosition;
 pub use values::specified::position::{GridAutoFlow, GridTemplateAreas};
@@ -40,7 +40,10 @@ impl Position {
 }
 
 impl ToCss for Position {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
         self.horizontal.to_css(dest)?;
         dest.write_str(" ")?;
         self.vertical.to_css(dest)