Add DocumentTiming metrics for "time to first text paint"

Source/platform/fonts/Font.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Holger Hans Peter Freyther
  *
  * 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
@@ skipping 119 matching lines @@
     int offsetForPositionForSimpleText(const TextRun&, float position, bool includePartialGlyphs) const;
     FloatRect selectionRectForSimpleText(const TextRun&, const FloatPoint&, int h, int from, int to, bool accountForGlyphBounds) const;
 
     bool getEmphasisMarkGlyphData(const AtomicString&, GlyphData&) const;
 
     float floatWidthForComplexText(const TextRun&, HashSet<const SimpleFontData*>* fallbackFonts, FloatRect* glyphBounds) const;
     int offsetForPositionForComplexText(const TextRun&, float position, bool includePartialGlyphs) const;
     FloatRect selectionRectForComplexText(const TextRun&, const FloatPoint&, int h, int from, int to) const;
 
     bool computeCanShapeWordByWord() const;
+    void reportFirstTextPaint() const;
 
     friend struct SimpleShaper;
 
 public:
     FontSelector* fontSelector() const;
 
     void willUseFontData(UChar32) const;
 
     bool loadingCustomFonts() const;
     bool isFallbackValid() const;
 
 private:
     bool shouldSkipDrawing() const
     {
         return m_fontFallbackList && m_fontFallbackList->shouldSkipDrawing();
     }
 
     FontDescription m_fontDescription;
     mutable RefPtr<FontFallbackList> m_fontFallbackList;
     mutable unsigned m_canShapeWordByWord : 1;
     mutable unsigned m_shapeWordByWordComputed : 1;
+    mutable unsigned m_firstPaintReported : 1;
 };
 
 inline Font::~Font()
 {
 }
 
 inline const SimpleFontData* Font::primaryFont() const
 {
     ASSERT(m_fontFallbackList);
     return m_fontFallbackList->primarySimpleFontData(m_fontDescription);
@@ skipping 21 matching lines @@
     // if the distance to the next tab stop is less than that, advance an additional tab stop.
     if (distanceToTabStop < std::max(fontDescription().letterSpacing(), LayoutUnit::epsilon()))
         distanceToTabStop += baseTabWidth;
 
     return distanceToTabStop;
 }
 
 } // namespace blink
 
 #endif