Let collapsed border drawings be cacheable

Source/platform/graphics/paint/DisplayItem.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 "platform/graphics/paint/DisplayItem.h"
 
 namespace blink {
 
 struct SameSizeAsDisplayItem {
@@ skipping 35 matching lines @@
     if (type >= DisplayItem::Category##PaintPhaseFirst && type <= DisplayItem::Category##PaintPhaseLast) \
         return #Category + paintPhaseAsDebugString(type - DisplayItem::Category##PaintPhaseFirst);
 
 #define DEBUG_STRING_CASE(DisplayItemName) \
     case DisplayItem::DisplayItemName: return #DisplayItemName
 
 #define DEFAULT_CASE default: ASSERT_NOT_REACHED(); return "Unknown"
 
 static WTF::String specialDrawingTypeAsDebugString(DisplayItem::Type type)
 {
+    if (type >= DisplayItem::TableCollapsedBorderUnalignedBase) {
+        if (type <= DisplayItem::TableCollapsedBorderBase)
+            return "TableCollapsedBorderAlignment";
+        if (type <= DisplayItem::TableCollapsedBorderLast) {
+            StringBuilder sb;
+            sb.append("TableCollapsedBorder");
+            if (type & DisplayItem::TableCollapsedBorderTop)
+                sb.append("Top");
+            if (type & DisplayItem::TableCollapsedBorderRight)
+                sb.append("Right");
+            if (type & DisplayItem::TableCollapsedBorderBottom)
+                sb.append("Bottom");
+            if (type & DisplayItem::TableCollapsedBorderLeft)
+                sb.append("Left");
+            return sb.toString();
+        }
+    }
     switch (type) {
         DEBUG_STRING_CASE(BoxDecorationBackground);
         DEBUG_STRING_CASE(Caret);
         DEBUG_STRING_CASE(ColumnRules);
         DEBUG_STRING_CASE(DebugRedFill);
         DEBUG_STRING_CASE(DragImage);
         DEBUG_STRING_CASE(SVGImage);
         DEBUG_STRING_CASE(LinkHighlight);
         DEBUG_STRING_CASE(PageOverlay);
         DEBUG_STRING_CASE(PageWidgetDelegateBackgroundFallback);
@@ skipping 146 matching lines @@
     stringBuilder.append('"');
     if (m_skippedCache)
         stringBuilder.append(", skippedCache: true");
     if (m_scope)
         stringBuilder.append(String::format(", scope: %d", m_scope));
 }
 
 #endif
 
 } // namespace blink