[DO NOT COMMIT] Trace events for layout-based First Meaningful Paint detection

third_party/WebKit/Source/core/css/FontFaceSet.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 214 matching lines @@
     removeFromLoadingFonts(fontFace);
 }
 
 void FontFaceSet::loadError(FontFace* fontFace)
 {
     m_histogram.updateStatus(fontFace);
     m_failedFonts.append(fontFace);
     removeFromLoadingFonts(fontFace);
 }
 
+bool FontFaceSet::hasBlankText() const
+{
+    for (auto& fontFace : m_loadingFonts) {
+        if (fontFace->isBlank())
+            return true;
+    }
+    return false;
+}
+
 void FontFaceSet::addToLoadingFonts(FontFace* fontFace)
 {
     if (!m_isLoading) {
         m_isLoading = true;
         m_shouldFireLoadingEvent = true;
         if (m_ready->getState() != ReadyProperty::Pending)
             m_ready->reset();
         handlePendingEventsAndPromisesSoon();
     }
     m_loadingFonts.add(fontFace);
@@ skipping 256 matching lines @@
 
     return fonts;
 }
 
 void FontFaceSet::didLayout(Document& document)
 {
     if (FontFaceSet* fonts = static_cast<FontFaceSet*>(Supplement<Document>::from(document, supplementName())))
         fonts->didLayout();
 }
 
+bool FontFaceSet::hasBlankText(Document& document)
+{
+    if (FontFaceSet* fonts = static_cast<FontFaceSet*>(Supplement<Document>::from(document, supplementName())))
+        return fonts->hasBlankText();
+    return false;
+}
+
 FontFaceSetIterable::IterationSource* FontFaceSet::startIteration(ScriptState*, ExceptionState&)
 {
     // Setlike should iterate each item in insertion order, and items should
     // be keep on up to date. But since blink does not have a way to hook up CSS
     // modification, take a snapshot here, and make it ordered as follows.
     HeapVector<Member<FontFace>> fontFaces;
     if (inActiveDocumentContext()) {
         const HeapListHashSet<Member<FontFace>>& cssConnectedFaces = cssConnectedFontFaceList();
         fontFaces.reserveInitialCapacity(cssConnectedFaces.size() + m_nonCSSConnectedFaces.size());
         for (const auto& fontFace : cssConnectedFaces)
@@ skipping 19 matching lines @@
     visitor->trace(m_loadedFonts);
     visitor->trace(m_failedFonts);
     visitor->trace(m_nonCSSConnectedFaces);
     visitor->trace(m_asyncRunner);
     EventTargetWithInlineData::trace(visitor);
     Supplement<Document>::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink