servo: Merge #2320 - Prevent unused result warning in codegen. Always expect success for now (from glennw:codegen-warnings); r=jdm

Is it reasonable to always expect success here for now?

Fixes #2246.

Source-Repo: https://github.com/servo/servo
Source-Revision: 310d2a19bbc1b8933f05cbd77c79df155ac00d94

servo/src/components/script/dom/bindings/codegen/CodegenRust.py

@@ -5341,7 +5341,7 @@ class GlobalGenRoots():
             trace = [CGGeneric(string.Template('''impl JSTraceable for ${name} {
     fn trace(&self, tracer: *mut JSTracer) {
         unsafe {
-            self.encode(&mut *tracer);
+            self.encode(&mut *tracer).ok().expect("failed to encode");
         }
     }
 }