Fix the fallback object detection.

web/js-src/register-element.js

@@ -3,6 +3,32 @@
  */
 var private_registry = {};
 
+/**
+ * Lookup a previously registered custom element.
+ * 
+ * @param {string} element_name The internal element name, previously used to
+ * register the element with the private registry.
+ * 
+ * @returns {object|null} The element data in the registry, or null if there is
+ * no such element name registered.
+ * 
+ * The returned object will have `name`, `class`, and `internal_name`
+ * properties listing the external name, implementing class, and internal name
+ * respectively.
+ */
+export function lookup_element(element_name) {
+    let data = private_registry[element_name];
+    if (data !== undefined) {
+        return {
+            "internal_name": element_name,
+            "name": data.name,
+            "class": data.class
+        };
+    } else {
+        return null;
+    }
+}
+
 /**
  * Register a custom element.
  * 

web/js-src/ruffle-player.js

@@ -1,5 +1,6 @@
 import load_ruffle from "./load-ruffle";
 import ruffle_shadow_template from "./shadow-template";
+import { lookup_element } from "./register-element";
 
 export let FLASH_MIMETYPE = "application/x-shockwave-flash";
 export let FUTURESPLASH_MIMETYPE = "application/futuresplash";
@@ -61,13 +62,17 @@ export class RufflePlayer extends HTMLElement {
      */
     is_unused_fallback_object() {
         let parent = this.parentNode;
-        do {
-            if (parent.nodeName === "RUFFLE-OBJECT") {
-                return true;
-            }
+        let element = lookup_element("ruffle-object");
 
-            parent = parent.parentNode;
-        } while (parent != document);
+        if (element !== null) {
+            do {
+                if (parent.nodeName === element.name) {
+                    return true;
+                }
+
+                parent = parent.parentNode;
+            } while (parent != document);
+        }
 
         return false;
     }