Let collapsed border drawings be cacheable

Source/core/layout/LayoutTableCell.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 933 matching lines @@
     borderValues.append(borderValue);
 }
 
 void LayoutTableCell::collectBorderValues(LayoutTable::CollapsedBorderValues& borderValues)
 {
     CollapsedBorderValue startBorder = computeCollapsedStartBorder();
     CollapsedBorderValue endBorder = computeCollapsedEndBorder();
     CollapsedBorderValue beforeBorder = computeCollapsedBeforeBorder();
     CollapsedBorderValue afterBorder = computeCollapsedAfterBorder();
     LayoutTableSection* section = this->section();
-    section->setCachedCollapsedBorder(this, CBSStart, startBorder);
-    section->setCachedCollapsedBorder(this, CBSEnd, endBorder);
-    section->setCachedCollapsedBorder(this, CBSBefore, beforeBorder);
-    section->setCachedCollapsedBorder(this, CBSAfter, afterBorder);
+    bool changed = section->setCachedCollapsedBorder(this, CBSStart, startBorder);
+    changed |= section->setCachedCollapsedBorder(this, CBSEnd, endBorder);
+    changed |= section->setCachedCollapsedBorder(this, CBSBefore, beforeBorder);
+    changed |= section->setCachedCollapsedBorder(this, CBSAfter, afterBorder);
+
+    // In slimming paint mode, we need to invalidate all cells with collapsed border changed.
+    // FIXME: Need a way to invalidate/repaint the borders only. crbug.com/451090#c5.
+    if (changed && RuntimeEnabledFeatures::slimmingPaintEnabled())
+        invalidateDisplayItemClient(*this);
 
     addBorderStyle(borderValues, startBorder);
     addBorderStyle(borderValues, endBorder);
     addBorderStyle(borderValues, beforeBorder);
     addBorderStyle(borderValues, afterBorder);
 }
 
 static int compareBorderValuesForQSort(const void* pa, const void* pb)
 {
     const CollapsedBorderValue* a = static_cast<const CollapsedBorderValue*>(pa);
@@ skipping 58 matching lines @@
 
 LayoutTableCell* LayoutTableCell::createAnonymousWithParent(const LayoutObject* parent)
 {
     LayoutTableCell* newCell = LayoutTableCell::createAnonymous(&parent->document());
     RefPtr<ComputedStyle> newStyle = ComputedStyle::createAnonymousStyleWithDisplay(parent->styleRef(), TABLE_CELL);
     newCell->setStyle(newStyle.release());
     return newCell;
 }
 
 } // namespace blink