Generate scroll/clip display item hierarchy for SPv2

Source/platform/graphics/paint/DisplayItem.cpp

Index: Source/platform/graphics/paint/DisplayItem.cpp
diff --git a/Source/platform/graphics/paint/DisplayItem.cpp b/Source/platform/graphics/paint/DisplayItem.cpp
index 25b0bcf79e4bb6e243f672e6e88edb6c865b86af..21b7265d4ecb576df2391666d909168945cb0c55 100644
--- a/Source/platform/graphics/paint/DisplayItem.cpp
+++ b/Source/platform/graphics/paint/DisplayItem.cpp
@@ -127,6 +127,7 @@ static WTF::String clipTypeAsDebugString(DisplayItem::Type type)
     PAINT_PHASE_BASED_DEBUG_STRINGS(ClipLayerFragment);
 
     switch (type) {
+        DEBUG_STRING_CASE(ClipDescendantStackingContext);
         DEBUG_STRING_CASE(ClipFileUploadControlRect);
         DEBUG_STRING_CASE(ClipFrameToVisibleContentRect);
         DEBUG_STRING_CASE(ClipFrameScrollbars);
@@ -191,8 +192,7 @@ WTF::String DisplayItem::typeAsDebugString(Type type)
         DEBUG_STRING_CASE(EndClipPath);
         DEBUG_STRING_CASE(BeginFixedPosition);
         DEBUG_STRING_CASE(EndFixedPosition);
-        DEBUG_STRING_CASE(BeginFixedPositionContainer);
-        DEBUG_STRING_CASE(EndFixedPositionContainer);
+        DEBUG_STRING_CASE(FixedPositionContainer);
         DEBUG_STRING_CASE(BeginSubsequence);
         DEBUG_STRING_CASE(EndSubsequence);
         DEBUG_STRING_CASE(CachedSubsequence);