[librsvg: 7/22] Prepare trait Resolve for immutability later

[Federico Mena Quintero <federico src gnome org>]

commit f8f2f5574f18ecebea00a6c934f818a49cb5cb70
Author: Federico Mena Quintero <federico gnome org>
Date:   Tue Oct 1 11:39:24 2019 -0500

    Prepare trait Resolve for immutability later

 rsvg_internals/src/paint_server.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/rsvg_internals/src/paint_server.rs b/rsvg_internals/src/paint_server.rs
index e31deeec..f403f718 100644
--- a/rsvg_internals/src/paint_server.rs
+++ b/rsvg_internals/src/paint_server.rs
@@ -109,9 +109,9 @@ pub trait ResolvedPaintSource {
 pub trait Resolve {
     fn is_resolved(&self) -> bool;
 
-    fn resolve_from_fallback(&mut self, fallback: &Self);
+    fn resolve_from_fallback(&self, fallback: &Self) -> Self;
 
-    fn resolve_from_defaults(&mut self);
+    fn resolve_from_defaults(&self) -> Self;
 }
 
 #[cfg(test)]