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

Source/core/css/CSSFontFaceSource.cpp

 /*
  * Copyright (C) 2007, 2008, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 187 matching lines @@
                         fontDescription.isSyntheticBold(),
                         fontDescription.isSyntheticItalic());
                 }
             } else
 #endif
             {
                 // Create new FontPlatformData from our CGFontRef, point size and ATSFontRef.
                 if (!m_font->ensureCustomFontData())
                     return nullptr;
 
+                m_histograms.recordFallbackTime(m_font.get());
+
                 fontData = SimpleFontData::create(
                     m_font->platformDataFromCustomData(fontDescription.effectiveFontSize(),
                         fontDescription.isSyntheticBold(), fontDescription.isSyntheticItalic(),
                         fontDescription.orientation(), fontDescription.widthVariant()), CustomFontData::create(false));
             }
         } else {
 #if ENABLE(SVG_FONTS)
             // In-Document SVG Fonts
             if (m_svgFontFaceElement) {
                 fontData = SimpleFontData::create(
@@ skipping 60 matching lines @@
     if (m_face && m_font)
         m_face->beginLoadIfNeeded(this);
 }
 
 void CSSFontFaceSource::FontLoadHistograms::loadStarted()
 {
     if (!m_loadStartTime)
         m_loadStartTime = currentTimeMS();
 }
 
+void CSSFontFaceSource::FontLoadHistograms::fallbackFontPainted()
+{
+    if (!m_fallbackPaintTime)
+        m_fallbackPaintTime = currentTimeMS();
+}
+
 void CSSFontFaceSource::FontLoadHistograms::recordLocalFont(bool loadSuccess)
 {
     if (!m_loadStartTime) {
         blink::Platform::current()->histogramEnumeration("WebFont.LocalFontUsed", loadSuccess ? 1 : 0, 2);
         m_loadStartTime = -1; // Do not count this font again.
     }
 }
 
+void CSSFontFaceSource::FontLoadHistograms::recordFallbackTime(const FontResource* font)
+{
+    if (m_fallbackPaintTime > 0) {

[dglazkov, 2014/03/04 17:24:08]

Early return?

[Kunihiko Sakamoto, 2014/03/05 08:55:59]

Done.

+        int duration = static_cast<int>(currentTimeMS() - m_fallbackPaintTime);
+        blink::Platform::current()->histogramCustomCounts("WebFont.BlankTextShownTime", duration, 0, 10000, 50);
+        m_fallbackPaintTime = -1;
+    }
+}
+
 void CSSFontFaceSource::FontLoadHistograms::recordRemoteFont(const FontResource* font)
 {
     if (m_loadStartTime > 0 && font && !font->isLoading()) {
         int duration = static_cast<int>(currentTimeMS() - m_loadStartTime);
         blink::Platform::current()->histogramCustomCounts(histogramName(font), duration, 0, 10000, 50);
         m_loadStartTime = -1;
 
         enum { Miss, Hit, DataUrl, CacheHitEnumMax };
         int histogramValue = font->url().protocolIsData() ? DataUrl
             : font->response().wasCached() ? Hit
@@ skipping 13 matching lines @@
     if (size < 50 * 1024)
         return "WebFont.DownloadTime.1.10KBTo50KB";
     if (size < 100 * 1024)
         return "WebFont.DownloadTime.2.50KBTo100KB";
     if (size < 1024 * 1024)
         return "WebFont.DownloadTime.3.100KBTo1MB";
     return "WebFont.DownloadTime.4.Over1MB";
 }
 
 }