debug first paint in iframe

third_party/WebKit/Source/core/paint/PaintTiming.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 "core/paint/PaintTiming.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 86 matching lines @@
   m_firstMeaningfulPaint = stamp;
   TRACE_EVENT_MARK_WITH_TIMESTAMP1(
       "blink.user_timing", "firstMeaningfulPaint",
       TraceEvent::toTraceTimestamp(m_firstMeaningfulPaint), "frame", frame());
   notifyPaintTimingChanged();
 }
 
 void PaintTiming::notifyPaint(bool isFirstPaint,
                               bool textPainted,
                               bool imagePainted) {
+  fprintf(stderr, "%s\n", "notifyPaint");
+  fprintf(stderr, "%s\n", supplementable()->url().getString().ascii().data());
   if (isFirstPaint)
     markFirstPaint();
   if (textPainted)
     markFirstTextPaint();
   if (imagePainted)
     markFirstImagePaint();
   m_fmpDetector->notifyPaint();
 }
 
 DEFINE_TRACE(PaintTiming) {
@@ skipping 32 matching lines @@
   setFirstPaint(stamp);
   m_firstContentfulPaint = stamp;
   Performance* performance = getPerformanceInstance(frame());
   if (performance)
     performance->addFirstContentfulPaintTiming(m_firstContentfulPaint);
   TRACE_EVENT_INSTANT1("blink.user_timing,rail", "firstContentfulPaint",
                        TRACE_EVENT_SCOPE_PROCESS, "frame", frame());
 }
 
 }  // namespace blink