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

Source/core/css/FontFaceSet.cpp

 /*
  * Copyright (C) 2013 Google 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 155 matching lines @@
 
 void FontFaceSet::handlePendingEventsAndPromisesSoon()
 {
     // setPendingActivity() is unnecessary because m_asyncRunner will be
     // automatically stopped on destruction.
     m_asyncRunner.runAsync();
 }
 
 void FontFaceSet::didLayout()
 {
-    if (document()->frame()->isMainFrame())
+    if (document()->frame()->isMainFrame() && m_loadingFonts.isEmpty())
         m_histogram.record();
     if (!RuntimeEnabledFeatures::fontLoadEventsEnabled())
         return;
     if (!m_loadingFonts.isEmpty() || (!hasLoadedFonts() && m_readyResolvers.isEmpty()))
         return;
     handlePendingEventsAndPromisesSoon();
 }
 
 void FontFaceSet::handlePendingEventsAndPromises()
 {
@@ skipping 25 matching lines @@
 }
 
 void FontFaceSet::beginFontLoading(FontFace* fontFace)
 {
     m_histogram.incrementCount();
     addToLoadingFonts(fontFace);
 }
 
 void FontFaceSet::fontLoaded(FontFace* fontFace)
 {
+    m_histogram.updateStatus(fontFace);
     if (RuntimeEnabledFeatures::fontLoadEventsEnabled())
         m_loadedFonts.append(fontFace);
     removeFromLoadingFonts(fontFace);
 }
 
 void FontFaceSet::loadError(FontFace* fontFace)
 {
+    m_histogram.updateStatus(fontFace);
     if (RuntimeEnabledFeatures::fontLoadEventsEnabled())
         m_failedFonts.append(fontFace);
     removeFromLoadingFonts(fontFace);
 }
 
 void FontFaceSet::addToLoadingFonts(PassRefPtr<FontFace> fontFace)
 {
     if (RuntimeEnabledFeatures::fontLoadEventsEnabled() && m_loadingFonts.isEmpty() && !hasLoadedFonts()) {
         m_shouldFireLoadingEvent = true;
         handlePendingEventsAndPromisesSoon();
@@ skipping 263 matching lines @@
         CSSPropertyValue(CSSPropertyLineHeight, *parsedStyle),
     };
     StyleResolver& styleResolver = document()->ensureStyleResolver();
     styleResolver.applyPropertiesToStyle(properties, WTF_ARRAY_LENGTH(properties), style.get());
 
     font = style->font();
     font.update(document()->styleEngine()->fontSelector());
     return true;
 }
 
+void FontFaceSet::FontLoadHistogram::updateStatus(FontFace* fontFace)
+{
+    if (m_status == Reported)
+        return;
+    if (fontFace->hadBlankText())
+        m_status = HadBlankText;
+    else if (m_status == NoWebFonts)
+        m_status = DidNotHaveBlankText;
+}
+
 void FontFaceSet::FontLoadHistogram::record()
 {
-    if (m_recorded)
-        return;
-    m_recorded = true;
-    blink::Platform::current()->histogramCustomCounts("WebFont.WebFontsInPage", m_count, 1, 100, 50);
+    if (!m_recorded) {
+        m_recorded = true;
+        blink::Platform::current()->histogramCustomCounts("WebFont.WebFontsInPage", m_count, 1, 100, 50);
+    }
+    if (m_status == HadBlankText || m_status == DidNotHaveBlankText) {
+        blink::Platform::current()->histogramEnumeration("WebFont.HadBlankText", m_status == HadBlankText ? 1 : 0, 2);
+        m_status = Reported;
+    }
 }
 
 static const char* supplementName()
 {
     return "FontFaceSet";
 }
 
 PassRefPtr<FontFaceSet> FontFaceSet::from(Document& document)
 {
     RefPtr<FontFaceSet> fonts = static_cast<FontFaceSet*>(SupplementType::from(document, supplementName()));
     if (!fonts) {
         fonts = FontFaceSet::create(document);
         SupplementType::provideTo(document, supplementName(), fonts);
     }
 
     return fonts.release();
 }
 
 void FontFaceSet::didLayout(Document& document)
 {
     if (FontFaceSet* fonts = static_cast<FontFaceSet*>(SupplementType::from(document, supplementName())))
         fonts->didLayout();
 }
 
 
 } // namespace WebCore