Statistics of LayoutBox rare data reasons

third_party/WebKit/Source/core/paint/BoxPaintInvalidator.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/BoxPaintInvalidator.h"
 
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/paint/ObjectPaintInvalidator.h"
@@ skipping 281 matching lines @@
   // Don't save old box geometries if the paint rect is empty because we'll
   // fully invalidate once the paint rect becomes non-empty.
   if (m_box.visualRect().isEmpty())
     return false;
 
   if (m_box.paintedOutputOfObjectHasNoEffectRegardlessOfSize())
     return false;
 
   const ComputedStyle& style = m_box.styleRef();
 
+  if (m_box.contentBoxRect() != m_box.borderBoxRect())
+    m_box.m_rareStat.addReason(ReasonLBContentBoxDiff);
+  if (m_box.layoutOverflowRect() != m_box.borderBoxRect())
+    m_box.m_rareStat.addReason(ReasonLBLayoutOverflowDiff);
+
   // Background and mask layers can depend on other boxes than border box. See
   // crbug.com/490533
   if ((style.backgroundLayers().thisOrNextLayersUseContentBox() ||
        style.maskLayers().thisOrNextLayersUseContentBox()) &&
       m_box.contentBoxRect().size() != m_box.size())
     return true;
   if ((backgroundGeometryDependsOnLayoutOverflowRect() ||
        backgroundPaintsOntoScrollingContentsLayer()) &&
       m_box.layoutOverflowRect() != m_box.borderBoxRect())
     return true;
 
   return false;
 }
 
 void BoxPaintInvalidator::savePreviousBoxGeometriesIfNeeded() {
   m_box.getMutableForPainting().savePreviousSize();
 
   if (needsToSavePreviousContentBoxSizeOrLayoutOverflowRect()) {
     m_box.getMutableForPainting()
         .savePreviousContentBoxSizeAndLayoutOverflowRect();
   } else {
     m_box.getMutableForPainting()
         .clearPreviousContentBoxSizeAndLayoutOverflowRect();
   }
 }
 
 }  // namespace blink