Remove Overlay Scrollbar if not scrollable along the axis

Source/core/rendering/RenderLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 988 matching lines @@
         m_scrollCorner = nullptr;
     }
 }
 
 void RenderLayerScrollableArea::paintOverflowControls(GraphicsContext* context, const IntPoint& paintOffset, const IntRect& damageRect, bool paintingOverlayControls)
 {
     // Don't do anything if we have no overflow.
     if (!box().hasOverflowClip())
         return;
 
+    if (hasOverlayScrollbars()) {
+        if (!scrollSize(HorizontalScrollbar))
+            destroyScrollbar(HorizontalScrollbar);
+        if (!scrollSize(VerticalScrollbar))
+            destroyScrollbar(VerticalScrollbar);
+    }
+
     IntPoint adjustedPaintOffset = paintOffset;
     if (paintingOverlayControls)
         adjustedPaintOffset = m_cachedOverlayScrollbarOffset;
 
     // Move the scrollbar widgets if necessary. We normally move and resize widgets during layout,
     // but sometimes widgets can move without layout occurring (most notably when you scroll a
     // document that contains fixed positioned elements).
     positionOverflowControls(toIntSize(adjustedPaintOffset));
 
     // Overlay scrollbars paint in a second pass through the layer tree so that they will paint
@@ skipping 450 matching lines @@
 void RenderLayerScrollableArea::setTopmostScrollChild(RenderLayer* scrollChild)
 {
     // We only want to track the topmost scroll child for scrollable areas with
     // overlay scrollbars.
     if (!hasOverlayScrollbars())
         return;
     m_nextTopmostScrollChild = scrollChild;
 }
 
 } // namespace blink