Implement JSTraceable for more types.

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

@@ -4103,6 +4103,7 @@ class CGUnionStruct(CGThing):
             % (self.type, v["name"]) for v in templateVars
         ]
         return ("""\
+#[derive(JSTraceable)]
 pub enum %s {
 %s
 }
@@ -5881,6 +5882,7 @@ class CGDictionary(CGThing):
                        for m in self.memberInfo]
 
         return (string.Template(
+                "#[derive(JSTraceable)]\n"
                 "pub struct ${selfName} {\n" +
                 "${inheritance}" +
                 "\n".join(memberDecls) + "\n" +

components/script/dom/bindings/js.rs

@@ -642,3 +642,9 @@ impl<T: DomObject> Drop for Root<T> {
         }
     }
 }
+
+unsafe impl<T: DomObject> JSTraceable for Root<T> {
+    unsafe fn trace(&self, _: *mut JSTracer) {
+        // Already traced.
+    }
+}

components/script/dom/bindings/mozmap.rs

@@ -23,7 +23,7 @@ use std::collections::HashMap;
 use std::ops::Deref;
 
 /// The `MozMap` (open-ended dictionary) type.
-#[derive(Clone)]
+#[derive(Clone, JSTraceable)]
 pub struct MozMap<T> {
     map: HashMap<DOMString, T>,
 }