Add DocumentTiming metrics for "time to first text paint"

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index b0d729f2f837f452c5c3dd0344440ca3d4aa6239..a7c010961726bced1c6da357368aa6a2627a55de 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1915,6 +1915,18 @@ void Document::layoutUpdated()
     }
 }
 
+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));