Enforce FirstContentfulPaint <= FirstMeaningfulPaint

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/dom/TaskRunnerHelper.h"
 #include "core/paint/PaintTiming.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
@@ skipping 104 matching lines @@
   m_networkStableTimer.startOneShot(kSecondsWithoutNetworkActivityThreshold,
                                     BLINK_FROM_HERE);
 }
 
 void FirstMeaningfulPaintDetector::networkStableTimerFired(TimerBase*) {
   if (m_state == Reported || !document() ||
       document()->fetcher()->hasPendingRequest() ||
       !m_paintTiming->firstContentfulPaint())
     return;
 
-  if (m_provisionalFirstMeaningfulPaint)
-    m_paintTiming->setFirstMeaningfulPaint(m_provisionalFirstMeaningfulPaint);
+  if (m_provisionalFirstMeaningfulPaint) {
+    // Enforce FirstContentfulPaint <= FirstMeaningfulPaint.
+    double timestamp = std::max(m_provisionalFirstMeaningfulPaint,
+                                m_paintTiming->firstContentfulPaint());
+    m_paintTiming->setFirstMeaningfulPaint(timestamp);
+  }
   m_state = Reported;
 }
 
 DEFINE_TRACE(FirstMeaningfulPaintDetector) {
   visitor->trace(m_paintTiming);
 }
 
 }  // namespace blink