Add trace event for FirstMeaningfulPaint candidates

third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp

 // Copyright 2016 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 "core/paint/FirstMeaningfulPaintDetector.h"
 
 #include "core/css/FontFaceSet.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/paint/PaintTiming.h"
+#include "platform/TraceEvent.h"
 
 namespace blink {
 
 namespace {
 
 // Web fonts that laid out more than this number of characters block First
 // Meaningful Paint.
 const int kBlankCharactersThreshold = 200;
 
 // FirstMeaningfulPaintDetector stops observing layouts and reports First
@@ skipping 59 matching lines @@
 {
     if (m_state != NextPaintIsMeaningful)
         return;
 
     // Skip document background-only paints.
     if (m_paintTiming->firstPaint() == 0.0)
         return;
 
     m_provisionalFirstMeaningfulPaint = monotonicallyIncreasingTime();
     m_state = NextPaintIsNotMeaningful;
+
+    TRACE_EVENT_MARK_WITH_TIMESTAMP1("loading", "firstMeaningfulPaintCandidate", m_provisionalFirstMeaningfulPaint, "frame", document()->frame());
 }
 
 void FirstMeaningfulPaintDetector::checkNetworkStable()
 {
     DCHECK(document());
     if (m_state == Reported || document()->fetcher()->hasPendingRequest())
         return;
 
     m_networkStableTimer.startOneShot(kSecondsWithoutNetworkActivityThreshold, BLINK_FROM_HERE);
 }
 
 void FirstMeaningfulPaintDetector::networkStableTimerFired(TimerBase*)
 {
     if (m_state == Reported || !document() || document()->fetcher()->hasPendingRequest())
         return;
 
     if (m_provisionalFirstMeaningfulPaint)
         m_paintTiming->setFirstMeaningfulPaint(m_provisionalFirstMeaningfulPaint);
     m_state = Reported;
 }
 
 DEFINE_TRACE(FirstMeaningfulPaintDetector)
 {
     visitor->trace(m_paintTiming);
 }
 
 } // namespace blink