Add a new top-level inspector timeline event for the PrePaint step

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 2968 matching lines @@
       DCHECK(scroller->scrollAnchor());
       scroller->scrollAnchor()->adjust();
     }
   }
   m_anchoringAdjustmentQueue.clear();
 }
 
 void FrameView::prePaint() {
   TRACE_EVENT0("blink", "FrameView::prePaint");
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.PrePaint.UpdateTime");
+  TRACE_EVENT1("devtools.timeline", "PreparePaint", "data",
+               InspectorPreparePaintEvent::data(m_frame.get()));
 
   if (!m_paintController)
     m_paintController = PaintController::create();
 
   forAllNonThrottledFrameViews([](FrameView& frameView) {
     frameView.lifecycle().advanceTo(DocumentLifecycle::InPrePaint);
   });
 
   if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled())
     PrePaintTreeWalk().walk(*this);
@@ skipping 1903 matching lines @@
        reason < MainThreadScrollingReason::kMainThreadScrollingReasonCount;
        ++reason) {
     if (m_mainThreadScrollingReasonsCounter[reason] > 0) {
       reasons |= 1 << reason;
     }
   }
   return reasons;
 }
 
 }  // namespace blink