Add DocumentTiming metrics for "time to first text paint"

Source/core/dom/DocumentTiming.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/DocumentTiming.h"
 
 #include "core/dom/Document.h"
 #include "core/loader/DocumentLoader.h"
 #include "platform/TraceEvent.h"
 #include "wtf/RawPtr.h"
 
 namespace blink {
 
 DocumentTiming::DocumentTiming(Document& document)
     : m_domLoading(0.0)
     , m_domInteractive(0.0)
     , m_domContentLoadedEventStart(0.0)
     , m_domContentLoadedEventEnd(0.0)
     , m_domComplete(0.0)
     , m_firstLayout(0.0)
+    , m_firstNonBlankText(0.0)
+    , m_firstCustomFontText(0.0)
     , m_document(document)
 {
 }
 
 DEFINE_TRACE(DocumentTiming)
 {
     visitor->trace(m_document);
 }
 
 void DocumentTiming::notifyDocumentTimingChanged()
@@ skipping 37 matching lines @@
     notifyDocumentTimingChanged();
 }
 
 void DocumentTiming::markFirstLayout()
 {
     m_firstLayout = monotonicallyIncreasingTime();
     TRACE_EVENT_MARK_WITH_TIMESTAMP("blink.user_timing", "firstLayout", m_firstLayout);
     notifyDocumentTimingChanged();
 }
 
+void DocumentTiming::markFirstNonBlankText()
+{
+    m_firstNonBlankText = monotonicallyIncreasingTime();
+    TRACE_EVENT_MARK_WITH_TIMESTAMP("blink.user_timing", "firstNonBlankText", m_firstNonBlankText);
+    notifyDocumentTimingChanged();
+}
+
+void DocumentTiming::markFirstCustomFontText()
+{
+    m_firstCustomFontText = monotonicallyIncreasingTime();
+    TRACE_EVENT_MARK_WITH_TIMESTAMP("blink.user_timing", "firstCustomFontText", m_firstCustomFontText);
+    notifyDocumentTimingChanged();
+}
+
 } // namespace blink