Revert of Paint collapsed borders of a table as one display item

third_party/WebKit/Source/platform/graphics/paint/DisplayItem.h

 // 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.
 
 #ifndef DisplayItem_h
 #define DisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/ContiguousContainer.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
@@ skipping 92 matching lines @@
     kScrollbarForwardTrack,
     kScrollbarThumb,
     kScrollbarTickmarks,
     kScrollbarTrackBackground,
     kScrollbarCompositedScrollbar,
     kSelectionTint,
     kTableCellBackgroundFromColumnGroup,
     kTableCellBackgroundFromColumn,
     kTableCellBackgroundFromSection,
     kTableCellBackgroundFromRow,
-    kTableCollapsedBorders,
+    // Table collapsed borders can be painted together (e.g., left & top) but
+    // there are at most 4 phases of collapsed border painting for a single
+    // cell. To disambiguate these phases of collapsed border painting, a mask
+    // is used. TableCollapsedBorderBase can be larger than
+    // TableCollapsedBorderUnalignedBase to ensure the base lower bits are 0's.
+    kTableCollapsedBorderUnalignedBase,
+    kTableCollapsedBorderBase =
+        (((kTableCollapsedBorderUnalignedBase - 1) >> 4) + 1) << 4,
+    kTableCollapsedBorderLast = kTableCollapsedBorderBase + 0x0f,
     kTableSectionBoxShadowInset,
     kTableSectionBoxShadowNormal,
     kTableRowBoxShadowInset,
     kTableRowBoxShadowNormal,
     kVideoBitmap,
     kWebPlugin,
     kWebFont,
     kReflectionMask,
     kDrawingLast = kReflectionMask,
 
@@ skipping 63 matching lines @@
     kBeginClipPath,
     kEndClipPath,
 
     kSubsequence,
     kEndSubsequence,
 
     kUninitializedType,
     kTypeLast = kUninitializedType
   };
 
+  static_assert(kTableCollapsedBorderBase >= kTableCollapsedBorderUnalignedBase,
+                "TableCollapsedBorder types overlap with other types");
+  static_assert((kTableCollapsedBorderBase & 0xf) == 0,
+                "The lowest 4 bits of TableCollapsedBorderBase should be zero");
+  // Bits or'ed onto TableCollapsedBorderBase to generate a real table collapsed
+  // border type.
+  enum TableCollapsedBorderSides {
+    TableCollapsedBorderTop = 1 << 0,
+    TableCollapsedBorderRight = 1 << 1,
+    TableCollapsedBorderBottom = 1 << 2,
+    TableCollapsedBorderLeft = 1 << 3,
+  };
+
   DisplayItem(const DisplayItemClient& client, Type type, size_t derivedSize)
       : m_client(&client),
         m_type(type),
         m_derivedSize(derivedSize),
         m_skippedCache(false)
 #ifndef NDEBUG
         ,
         m_clientDebugString(client.debugName())
 #endif
   {
@@ skipping 194 matching lines @@
   bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
 #endif
 
  private:
   bool isEnd() const final { return true; }
 };
 
 }  // namespace blink
 
 #endif  // DisplayItem_h