Bug 1491846 GetFrameLoader inside child objects vtbls could not be resolved by linker. It looks like a clang bug, but requires closer look. I worked around it by having explicit forwards. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D6051

dom/html/HTMLObjectElement.h

@@ -243,6 +243,8 @@ public:
    */
   void StartObjectLoad(bool aNotify, bool aForceLoad);
 
+  NS_FORWARD_NSIFRAMELOADEROWNER(nsObjectLoadingContent::)
+
 protected:
   // Override for nsImageLoadingContent.
   nsIContent* AsContent() override { return this; }