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

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

 /*
  * Copyright (C) 2007, 2008, 2011 Apple 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 37 matching lines @@
 
     void setFontFace(CSSFontFace* face) { m_face = face; }
 
     PassRefPtr<SimpleFontData> getFontData(const FontDescription&);
 
     virtual bool isLocalFontAvailable(const FontDescription&) { return false; }
     virtual void beginLoadIfNeeded() { }
 
     // For UMA reporting
     virtual bool hadBlankText() { return false; }
+    virtual bool isBlank() { return false; }
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     CSSFontFaceSource();
     virtual PassRefPtr<SimpleFontData> createFontData(const FontDescription&) = 0;
 
     using FontDataTable = HashMap<unsigned, RefPtr<SimpleFontData>>; // The hash key is composed of size synthetic styles.
 
     Member<CSSFontFace> m_face; // Our owning font face.
     FontDataTable m_fontDataTable;
 };
 
 } // namespace blink
 
 #endif