style: Add new layer messages for passing motion path info.

This also includes the implementation of SetAnimatable, FromAnimatable,
and merge the final matrix with motion path.

Besides, we always use PathBuilderSkia for calculating the gfx::Path for
web-renderer.

Differential Revision: https://phabricator.services.mozilla.com/D50011

components/style/values/specified/svg_path.rs

@@ -46,7 +46,7 @@ impl SVGPathData {
 
     /// Create a normalized copy of this path by converting each relative
     /// command to an absolute command.
-    fn normalize(&self) -> Box<[PathCommand]> {
+    pub fn normalize(&self) -> Self {
         let mut state = PathTraversalState {
             subpath_start: CoordPair::new(0.0, 0.0),
             pos: CoordPair::new(0.0, 0.0),
@@ -56,7 +56,8 @@ impl SVGPathData {
             .iter()
             .map(|seg| seg.normalize(&mut state))
             .collect::<Vec<_>>();
-        result.into_boxed_slice()
+
+        SVGPathData(crate::ArcSlice::from_iter(result.into_iter()))
     }
 }
 
@@ -119,8 +120,9 @@ impl Animate for SVGPathData {
         // re-normalize again.
         let result = self
             .normalize()
+            .0
             .iter()
-            .zip(other.normalize().iter())
+            .zip(other.normalize().0.iter())
             .map(|(a, b)| a.animate(&b, procedure))
             .collect::<Result<Vec<_>, _>>()?;
 
@@ -134,8 +136,9 @@ impl ComputeSquaredDistance for SVGPathData {
             return Err(());
         }
         self.normalize()
+            .0
             .iter()
-            .zip(other.normalize().iter())
+            .zip(other.normalize().0.iter())
             .map(|(this, other)| this.compute_squared_distance(&other))
             .sum()
     }