[librsvg/librsvg-2.44] Add missing comment

[Federico Mena Quintero <federico src gnome org>]

commit 3b5ee206e425aac82e2a0ea5467a8feec742d0eb
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Sep 21 12:29:21 2018 -0500

    Add missing comment

 rsvg_internals/src/filters/context.rs | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/rsvg_internals/src/filters/context.rs b/rsvg_internals/src/filters/context.rs
index 5beb6a82..b75a4a1e 100644
--- a/rsvg_internals/src/filters/context.rs
+++ b/rsvg_internals/src/filters/context.rs
@@ -437,6 +437,7 @@ impl FilterContext {
             rv
         } else {
             f(Box::new(|length: &Length| {
+                // Filters use the properties of the target node.
                 length.normalize(
                     &self.computed_from_node_being_filtered,
                     &draw_ctx.get_view_params(),