Paint collapsed borders of a table as one display item

third_party/WebKit/Source/core/layout/LayoutTable.h

Index: third_party/WebKit/Source/core/layout/LayoutTable.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutTable.h b/third_party/WebKit/Source/core/layout/LayoutTable.h
index adc7a6be3d99262fb577a9743930eba1a6a9ec7d..5f1bcde3bc71a28969cea278b6abbfa04566289b 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTable.h
+++ b/third_party/WebKit/Source/core/layout/LayoutTable.h
@@ -29,7 +29,9 @@
 #include "core/CSSPropertyNames.h"
 #include "core/CoreExport.h"
 #include "core/layout/LayoutBlock.h"
+#include "core/paint/PaintResult.h"
 #include "core/style/CollapsedBorderValue.h"
+#include "platform/graphics/paint/CullRect.h"
 #include "wtf/Vector.h"
 #include <memory>
 
@@ -375,7 +377,6 @@ class CORE_EXPORT LayoutTable final : public LayoutBlock {
   LayoutTableCell* cellBefore(const LayoutTableCell*) const;
   LayoutTableCell* cellAfter(const LayoutTableCell*) const;
 
-  typedef Vector<CollapsedBorderValue> CollapsedBorderValues;
   void invalidateCollapsedBorders();
 
   bool hasSections() const { return m_head || m_foot || m_firstBody; }
@@ -405,9 +406,23 @@ class CORE_EXPORT LayoutTable final : public LayoutBlock {
 
   void paintMask(const PaintInfo&, const LayoutPoint&) const final;
 
-  const CollapsedBorderValues& collapsedBorders() const {
-    ASSERT(m_collapsedBordersValid);
-    return m_collapsedBorders;
+  struct CollapsedBordersInfo {
+    explicit CollapsedBordersInfo(const Vector<CollapsedBorderValue>& values)
+        : values(std::move(values)) {}
+
+    PaintResult lastPaintResult = FullyPainted;
+    CullRect lastPaintRect;
+    const Vector<CollapsedBorderValue> values;
+  };
+
+  bool hasCollapsedBorders() const {
+    DCHECK(m_collapsedBordersValid);
+    DCHECK(!m_collapsedBordersInfo || collapseBorders());
+    return !!m_collapsedBordersInfo;
+  }
+  CollapsedBordersInfo& getCollapsedBordersInfo() const {
+    DCHECK(hasCollapsedBorders());
+    return *m_collapsedBordersInfo;
   }
 
   void subtractCaptionRect(LayoutRect&) const;
@@ -550,7 +565,7 @@ class CORE_EXPORT LayoutTable final : public LayoutBlock {
   // need to compare a cells border against all the adjoining cells, rows,
   // row groups, column, column groups and table. Thus we cache them in this
   // field.
-  CollapsedBorderValues m_collapsedBorders;
+  std::unique_ptr<CollapsedBordersInfo> m_collapsedBordersInfo;
   bool m_collapsedBordersValid : 1;
 
   mutable bool m_hasColElements : 1;