Add DocumentTiming metrics for "time to first text paint"

Source/platform/fonts/Font.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (c) 2007, 2008, 2010 Google Inc. All rights reserved.
  *
  * 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 125 matching lines @@
     return width;
 }
 
 void Font::drawText(SkCanvas* canvas, const TextRunPaintInfo& runInfo,
     const FloatPoint& point, float deviceScaleFactor, const SkPaint& paint) const
 {
     // Don't draw anything while we are using custom fonts that are in the process of loading.
     if (shouldSkipDrawing())
         return;
 
+    if (fontSelector())

[drott, 2015/09/16 07:26:20]

If I am not mistaken, this keeps calling reportFirstNonBlankText reporting, and
calling up to m_document of CSSFontSelector for every draw call. The
Font::drawText is a highly performance sensitive function - I would prefer not
to introduce additional callback hooks into it.

[Kunihiko Sakamoto, 2015/09/17 08:36:10]

That's right - I optimistically assumed the function call cost would be small
compared to actual font drawing.
Added a flag so that calling up to Document occurs at most once per Font
instance.

+        fontSelector()->reportFirstNonBlankText(m_fontFallbackList->hasCustomFont());
+
     if (runInfo.cachedTextBlob && runInfo.cachedTextBlob->get()) {
         // we have a pre-cached blob -- happy joy!
         drawTextBlob(canvas, paint, runInfo.cachedTextBlob->get(), point.data());
         return;
     }
 
     GlyphBuffer glyphBuffer;
     buildGlyphBuffer(runInfo, glyphBuffer);
 
     drawGlyphBuffer(canvas, paint, runInfo, glyphBuffer, point, deviceScaleFactor);
 }
 
 void Font::drawBidiText(SkCanvas* canvas, const TextRunPaintInfo& runInfo, const FloatPoint& point, CustomFontNotReadyAction customFontNotReadyAction, float deviceScaleFactor, const SkPaint& paint) const
 {
     // Don't draw anything while we are using custom fonts that are in the process of loading,
     // except if the 'force' argument is set to true (in which case it will use a fallback
     // font).
     if (shouldSkipDrawing() && customFontNotReadyAction == DoNotPaintIfFontNotReady)
         return;
 
+    if (fontSelector())

[drott, 2015/09/16 07:26:20]

Dito.

+        fontSelector()->reportFirstNonBlankText(m_fontFallbackList->hasCustomFont());
+
     // sub-run painting is not supported for Bidi text.
     const TextRun& run = runInfo.run;
     ASSERT((runInfo.from == 0) && (runInfo.to == run.length()));
     BidiResolver<TextRunIterator, BidiCharacterRun> bidiResolver;
     bidiResolver.setStatus(BidiStatus(run.direction(), run.directionalOverride()));
     bidiResolver.setPositionIgnoringNestedIsolates(TextRunIterator(&run, 0));
 
     // FIXME: This ownership should be reversed. We should pass BidiRunList
     // to BidiResolver in createBidiRunsForLine.
     BidiRunList<BidiCharacterRun>& bidiRuns = bidiResolver.runs();
@@ skipping 645 matching lines @@
 {
     return m_fontFallbackList && m_fontFallbackList->loadingCustomFonts();
 }
 
 bool Font::isFallbackValid() const
 {
     return !m_fontFallbackList || m_fontFallbackList->isValid();
 }
 
 } // namespace blink