Add DocumentTiming metrics for "time to first text paint"

Source/platform/fonts/FontFallbackList.cpp

 /*
  * Copyright (C) 2006 Apple Computer, 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
@@ skipping 28 matching lines @@
 namespace blink {
 
 FontFallbackList::FontFallbackList()
     : m_pageZero(0)
     , m_cachedPrimarySimpleFontData(0)
     , m_fontSelector(nullptr)
     , m_fontSelectorVersion(0)
     , m_familyIndex(0)
     , m_generation(FontCache::fontCache()->generation())
     , m_hasLoadingFallback(false)
+    , m_hasCustomFont(false)
 {
 }
 
 void FontFallbackList::invalidate(PassRefPtrWillBeRawPtr<FontSelector> fontSelector)
 {
     releaseFontData();
     m_fontList.clear();
     m_pageZero = 0;
     m_pages.clear();
     m_cachedPrimarySimpleFontData = 0;
     m_familyIndex = 0;
     m_hasLoadingFallback = false;
+    m_hasCustomFont = false;
     if (m_fontSelector != fontSelector)
         m_fontSelector = fontSelector;
     m_fontSelectorVersion = m_fontSelector ? m_fontSelector->version() : 0;
     m_generation = FontCache::fontCache()->generation();
     m_cachingWordShaper.clear();
 }
 
 void FontFallbackList::releaseFontData()
 {
     unsigned numFonts = m_fontList.size();
@@ skipping 13 matching lines @@
     unsigned numFonts = m_fontList.size();
     for (unsigned i = 0; i < numFonts; ++i) {
         if (m_fontList[i]->isLoading())
             return true;
     }
     return false;
 }
 
 bool FontFallbackList::shouldSkipDrawing() const
 {
-    if (!m_hasLoadingFallback)
-        return false;
-
-    unsigned numFonts = m_fontList.size();
-    for (unsigned i = 0; i < numFonts; ++i) {
-        if (m_fontList[i]->shouldSkipDrawing())
-            return true;
+    if (m_hasLoadingFallback) {
+        unsigned numFonts = m_fontList.size();
+        for (unsigned i = 0; i < numFonts; ++i) {
+            if (m_fontList[i]->shouldSkipDrawing())
+                return true;
+        }
     }
+    if (m_fontSelector)
+        m_fontSelector->reportFirstNonBlankText(m_hasCustomFont);

[Bryan McQuade, 2015/09/15 17:24:17]

I'm still learning this code so I may be misunderstanding, but given that
shouldSkipDrawing is a const method, which from its method signature appears to
not have side effects, I worry a little bit about depending on when/where such a
method gets called to record the first non-blank text. Would it make sense to
move this to the code that is actually responsible for drawing text, perhaps
somewhere in the Font class?

[Kunihiko Sakamoto, 2015/09/16 05:37:03]

Agreed that reporting from shouldXXX is confusing. Moved this to the caller side
(Font::drawText is also a const method, but it having side effects may be less
counter-intuitive).

     return false;
 }
 
 const SimpleFontData* FontFallbackList::determinePrimarySimpleFontData(const FontDescription& fontDescription) const
 {
     bool shouldLoadCustomFont = true;
 
     for (unsigned fontIndex = 0; ; ++fontIndex) {
         const FontData* fontData = fontDataAt(fontDescription, fontIndex);
         if (!fontData) {
@@ skipping 92 matching lines @@
     // Ask the font cache for the font data.
     // We are obtaining this font for the first time.  We keep track of the families we've looked at before
     // in |m_familyIndex|, so that we never scan the same spot in the list twice.  getFontData will adjust our
     // |m_familyIndex| as it scans for the right font to make.
     ASSERT(FontCache::fontCache()->generation() == m_generation);
     RefPtr<FontData> result = getFontData(fontDescription, m_familyIndex);
     if (result) {
         m_fontList.append(result);
         if (result->isLoadingFallback())
             m_hasLoadingFallback = true;
+        if (result->isCustomFont())
+            m_hasCustomFont = true;
     }
     return result.get();
 }
 
 bool FontFallbackList::isValid() const
 {
     if (!m_fontSelector)
         return m_fontSelectorVersion == 0;
 
     return m_fontSelector->version() == m_fontSelectorVersion;
 }
 
 } // namespace blink