Add DocumentTiming metrics for "time to first text paint"

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1897 matching lines @@
     // The layout system may perform layouts with pending stylesheets. When
     // recording first layout time, we ignore these layouts, since painting is
     // suppressed for them. We're interested in tracking the time of the
     // first real or 'paintable' layout.
     if (isRenderingReady() && body() && !styleEngine().hasPendingSheets()) {
         if (!m_documentTiming.firstLayout())
             m_documentTiming.markFirstLayout();
     }
 }
 
+void Document::markFirstCustomFontText()
+{
+    if (!m_documentTiming.firstCustomFontText())
+        m_documentTiming.markFirstCustomFontText();
+}
+
+void Document::markFirstNonBlankText()
+{
+    if (!m_documentTiming.firstNonBlankText())
+        m_documentTiming.markFirstNonBlankText();
+}

[kinuko, 2015/09/15 05:25:08]

(If we start to feel these are too annoying let's consider moving these out of
Document class as you did in the first patch... for now this looks ok to me)

+
 void Document::setNeedsFocusedElementCheck()
 {
     setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::createWithExtraData(StyleChangeReason::PseudoClass, StyleChangeExtraData::Focus));
 }
 
 void Document::clearFocusedElementSoon()
 {
     if (!m_clearFocusedElementTimer.isActive())
         m_clearFocusedElementTimer.startOneShot(0, FROM_HERE);
 }
@@ skipping 3808 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     Document::WeakDocumentSet& set = Document::liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif