UMA histograms to measure whether / how long blank text is rendered for loading web fonts

Source/platform/fonts/CustomFontData.h

 /*
  * Copyright (C) 2013 Google, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 30 matching lines @@
     static PassRefPtr<CustomFontData> create(bool isLoadingFallback = false, FallbackVisibility visibility = VisibleFallback)
     {
         return adoptRef(new CustomFontData(isLoadingFallback, visibility));
     }
 
     virtual ~CustomFontData() { }
 
     virtual void beginLoadIfNeeded() const { };
     bool isLoading() const { return m_isLoadingFallback && m_isUsed; }
     bool isLoadingFallback() const { return m_isLoadingFallback; }
-    bool shouldSkipDrawing() const { return m_fallbackVisibility == InvisibleFallback && m_isUsed; }
+    virtual bool shouldSkipDrawing() const { return false; }
 
     virtual bool isSVGFont() const { return false; }
     virtual void initializeFontData(SimpleFontData*, float) { }
     virtual float widthForSVGGlyph(Glyph, float) const { return 0.0f; }
     virtual bool fillSVGGlyphPage(GlyphPage*, unsigned, unsigned, UChar*, unsigned, const SimpleFontData*) const { return false; }
     virtual bool applySVGGlyphSelection(WidthIterator&, GlyphData&, bool, int, unsigned&) const { return false; }
 
     virtual void setCSSFontFaceSource(CSSFontFaceSource* source) { ASSERT_NOT_REACHED(); }
     virtual void clearCSSFontFaceSource() { }
 
 protected:
     CustomFontData(bool isLoadingFallback, FallbackVisibility visibility = VisibleFallback)
         : m_isLoadingFallback(isLoadingFallback)
         , m_fallbackVisibility(visibility)
         , m_isUsed(false)
     {
     }
 
     bool m_isLoadingFallback;
     FallbackVisibility m_fallbackVisibility;
     mutable bool m_isUsed;
 };
 
 }
 
 #endif // CustomFontData_h