Clip scrollbars to box bounds when they don't fit.

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 109 matching lines @@
         ClipFrameToVisibleContentRect,
         ClipFrameScrollbars,
         ClipLayerBackground,
         ClipLayerColumnBounds,
         ClipLayerFilter,
         ClipLayerForeground,
         ClipLayerParent,
         ClipLayerOverflowControls,
         ClipNodeImage,
         ClipPopupListBoxFrame,
+        ClipScrollbarsToBoxBounds,
         ClipSelectionImage,
         PageWidgetDelegateClip,
         ClipPrintedPage,
         ClipLast = ClipPrintedPage,
 
         EndClipFirst,
         EndClipLast = EndClipFirst + ClipLast - ClipFirst,
 
         FloatClipFirst,
         FloatClipPaintPhaseFirst = FloatClipFirst,
@@ skipping 248 matching lines @@
     bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
 #endif
 
 private:
     bool isEnd() const final { return true; }
 };
 
 } // namespace blink
 
 #endif // DisplayItem_h