--- a/dom/base/nsContentSink.cpp
+++ b/dom/base/nsContentSink.cpp
@@ -1230,16 +1230,19 @@ void
 nsContentSink::ScrollToRef()
 {
   mDocument->ScrollToRef();
 }
 
 void
 nsContentSink::StartLayout(bool aIgnorePendingSheets)
 {
+  AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING("nsContentSink::StartLayout", LAYOUT,
+                                        mDocumentURI->GetSpecOrDefault());
+
   if (mLayoutStarted) {
     // Nothing to do here
     return;
   }
 
   mDeferredLayoutStart = true;
 
   if (!aIgnorePendingSheets && WaitForPendingSheets()) {