Let collapsed border drawings be cacheable

Source/platform/graphics/paint/DisplayItemTest.cpp

Index: Source/platform/graphics/paint/DisplayItemTest.cpp
diff --git a/Source/platform/graphics/paint/DisplayItemTest.cpp b/Source/platform/graphics/paint/DisplayItemTest.cpp
index 5a6b51298fdba765488870fb75e06847ad355bcf..98b23b556d74379ab703f3392283ab976a9616ce 100644
--- a/Source/platform/graphics/paint/DisplayItemTest.cpp
+++ b/Source/platform/graphics/paint/DisplayItemTest.cpp
@@ -14,6 +14,10 @@ namespace {
 TEST(DisplayItemTest, DebugStringsExist)
 {
     for (int type = 0; type <= DisplayItem::TypeLast; type++) {
+        DisplayItem::Type nonCachedType = DisplayItem::nonCachedType(static_cast<DisplayItem::Type>(type));
+        if (nonCachedType >= DisplayItem::TableCollapsedBorderUnalignedBase && nonCachedType <= DisplayItem::TableCollapsedBorderBase)
+            continue;
+
         String debugString = DisplayItem::typeAsDebugString(static_cast<DisplayItem::Type>(type));
         EXPECT_FALSE(debugString.isEmpty());
         EXPECT_NE("Unknown", debugString);