debug first paint in iframe

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 3138 matching lines @@
 
 void FrameView::notifyPaint(const PaintController& paintController) const {
   DCHECK(m_frame->document());
   PaintTiming::from(*m_frame->document())
       .notifyPaint(paintController.firstPainted(),
                    paintController.textPainted(),
                    paintController.imagePainted());
 }
 
 void FrameView::paintTree() {
+  fprintf(stderr, "%s\n", "paintTree");
   TRACE_EVENT0("blink", "FrameView::paintTree");
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.Paint.UpdateTime");
 
   ASSERT(frame() == page()->mainFrame() ||
          (!frame().tree().parent()->isLocalFrame()));
 
   LayoutViewItem view = layoutViewItem();
   ASSERT(!view.isNull());
   forAllNonThrottledFrameViews([](FrameView& frameView) {
     frameView.lifecycle().advanceTo(DocumentLifecycle::InPaint);
@@ skipping 2072 matching lines @@
 void FrameView::setAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   m_animationHost = std::move(host);
 }
 
 LayoutUnit FrameView::caretWidth() const {
   return LayoutUnit(getHostWindow()->windowToViewportScalar(1));
 }
 
 }  // namespace blink