--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -3463,16 +3463,21 @@ public:
   void ListTag(FILE* out) const {
     ListTag(out, this);
   }
   static void ListTag(FILE* out, const nsIFrame* aFrame) {
     nsAutoCString t;
     ListTag(t, aFrame);
     fputs(t.get(), out);
   }
+  static void ListTag(FILE* out, const nsFrameList& aFrameList) {
+    for (nsIFrame* frame : aFrameList) {
+      ListTag(out, frame);
+    }
+  }
   void ListTag(nsACString& aTo) const;
   nsAutoCString ListTag() const {
     nsAutoCString tag;
     ListTag(tag);
     return tag;
   }
   static void ListTag(nsACString& aTo, const nsIFrame* aFrame);
   void ListGeneric(nsACString& aTo, const char* aPrefix = "", uint32_t aFlags = 0) const;