Fix FontFaceSet state getting stuck at loading

third_party/WebKit/Source/core/css/FontFace.h

Index: third_party/WebKit/Source/core/css/FontFace.h
diff --git a/third_party/WebKit/Source/core/css/FontFace.h b/third_party/WebKit/Source/core/css/FontFace.h
index d5b17d6765c1eba91d831d79d85300a6f6fbfaaf..f6e5b45c205caa07789a467f2a4252ad288a017e 100644
--- a/third_party/WebKit/Source/core/css/FontFace.h
+++ b/third_party/WebKit/Source/core/css/FontFace.h
@@ -101,7 +101,7 @@ public:
 
     bool hadBlankText() const;
 
-    class LoadFontCallback : public GarbageCollectedFinalized<LoadFontCallback> {
+    class LoadFontCallback : public GarbageCollectedMixin {
     public:
         virtual ~LoadFontCallback() { }
         virtual void notifyLoaded(FontFace*) = 0;
@@ -109,6 +109,7 @@ public:
         DEFINE_INLINE_VIRTUAL_TRACE() { }
     };
     void loadWithCallback(LoadFontCallback*, ExecutionContext*);
+    void addCallback(LoadFontCallback*);
 
     // ScriptWrappable:
     bool hasPendingActivity() const final;