Strengthen the LayoutGrid dirtiness asserts.

Source/core/paint/GridPainter.cpp

 // Copyright 2014 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 "config.h"
 #include "core/paint/GridPainter.h"
 
 #include "core/layout/LayoutGrid.h"
 #include "core/paint/BlockPainter.h"
 #include "core/paint/PaintInfo.h"
@@ skipping 23 matching lines @@
         if (firstChild.first->style()->order() != secondChild.first->style()->order())
             return firstChild.first->style()->order() < secondChild.first->style()->order();
 
         return firstChild.second < secondChild.second;
     }
 };
 
 void GridPainter::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     ASSERT(!m_layoutGrid.needsLayout());
-    ASSERT_WITH_SECURITY_IMPLICATION(!m_layoutGrid.gridIsDirty());
 
     LayoutRect localPaintInvalidationRect = LayoutRect(paintInfo.rect);
     localPaintInvalidationRect.moveBy(-paintOffset);
 
     GridSpan dirtiedColumns = dirtiedGridAreas(m_layoutGrid.columnPositions(), localPaintInvalidationRect.x(), localPaintInvalidationRect.maxX());
     GridSpan dirtiedRows = dirtiedGridAreas(m_layoutGrid.rowPositions(), localPaintInvalidationRect.y(), localPaintInvalidationRect.maxY());
 
     Vector<std::pair<LayoutBox*, size_t>> gridItemsToBePainted;
 
     for (GridSpan::iterator row = dirtiedRows.begin(); row != dirtiedRows.end(); ++row) {
@@ skipping 20 matching lines @@
         LayoutBox* current = gridItemAndPaintIndex.first;
         if (current == previous)
             continue;
 
         BlockPainter(m_layoutGrid).paintChildAsInlineBlock(*current, paintInfo, paintOffset);
         previous = current;
     }
 }
 
 } // namespace blink