Generate scroll/clip display item hierarchy for SPv2

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 95 matching lines @@
         CachedDrawingFirst,
         CachedDrawingLast = CachedDrawingFirst + DrawingLast - DrawingFirst,
 
         ClipFirst,
         ClipBoxPaintPhaseFirst = ClipFirst,
         ClipBoxPaintPhaseLast = ClipBoxPaintPhaseFirst + PaintPhaseMax,
         ClipColumnBoundsPaintPhaseFirst,
         ClipColumnBoundsPaintPhaseLast = ClipColumnBoundsPaintPhaseFirst + PaintPhaseMax,
         ClipLayerFragmentPaintPhaseFirst,
         ClipLayerFragmentPaintPhaseLast = ClipLayerFragmentPaintPhaseFirst + PaintPhaseMax,
+        ClipDescendantStackingContext,
         ClipFileUploadControlRect,
         ClipFrameToVisibleContentRect,
         ClipFrameScrollbars,
         ClipLayerBackground,
         ClipLayerColumnBounds,
         ClipLayerFilter,
         ClipLayerForeground,
         ClipLayerParent,
         ClipLayerOverflowControls,
         ClipNodeImage,
@@ skipping 250 matching lines @@
     bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
 #endif
 
 private:
     bool isEnd() const final { return true; }
 };
 
 } // namespace blink
 
 #endif // DisplayItem_h