Add FIXME for font-size animated value

components/style/values/computed/font.rs

@@ -76,6 +76,10 @@ impl ToCss for FontSize {
     }
 }
 
+/// XXXManishearth it might be better to
+/// animate this as computed, however this complicates
+/// clamping and might not be the right thing to do.
+/// We should figure it out.
 impl ToAnimatedValue for FontSize {
     type AnimatedValue = NonNegativeLength;
 

components/style/values/computed/length.rs

@@ -792,7 +792,7 @@ impl NonNegativeLength {
     }
 
     #[inline]
-    /// Ensures it is positive
+    /// Ensures it is non negative
     pub fn clamp(self) -> Self {
         if (self.0).0 < 0. {
             Self::zero()