Invalidate paint when allocating a DeprecatedPaintLayer.

Source/core/layout/LayoutFlowThread.cpp

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 160 matching lines @@
     dirtyRectInMulticolContainer.moveBy(location());
 
     for (LayoutMultiColumnSetList::const_iterator iter = m_multiColumnSetList.begin(); iter != m_multiColumnSetList.end(); ++iter) {
         LayoutMultiColumnSet* columnSet = *iter;
         columnSet->collectLayerFragments(layerFragments, layerBoundingBox, dirtyRectInMulticolContainer);
     }
 }
 
 LayoutRect LayoutFlowThread::fragmentsBoundingBox(const LayoutRect& layerBoundingBox) const
 {
-    ASSERT(!m_columnSetsInvalidated);
+    ASSERT(!RuntimeEnabledFeatures::slimmingPaintV2Enabled() || !m_columnSetsInvalidated);
 
     LayoutRect result;
     for (auto* columnSet : m_multiColumnSetList)
         result.unite(columnSet->fragmentsBoundingBox(layerBoundingBox));
 
     return result;
 }
 
 void LayoutFlowThread::MultiColumnSetSearchAdapter::collectIfNeeded(const MultiColumnSetInterval& interval)
 {
     if (m_result)
         return;
     if (interval.low() <= m_offset && interval.high() > m_offset)
         m_result = interval.data();
 }
 
 } // namespace blink