Only paint the background onto the scrolling contents layer if we have a scrolling contents layer.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.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@gmail.com>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1479 matching lines @@
         return false;
 
     Node* node = layer->enclosingNode();
     if (node && node->isElementNode() && (toElement(node)->compositorMutableProperties() & (CompositorMutableProperty::kScrollTop | CompositorMutableProperty::kScrollLeft)))
         return true;
 
     // TODO(schenney): LCD Text also requires integer scroll offsets for the layer. While we
     // use integer scroll offsets locally when !layer->compositor()->preferCompositingToLCDTextEnabled(),
     // we do not check offsets accumulated from the root (including translates). crbug.com/644833
     bool backgroundSupportsLCDText = RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled()
-        && layer->shouldPaintBackgroundOntoScrollingContentsLayer()
+        && layer->canPaintBackgroundOntoScrollingContentsLayer()
         && layer->backgroundIsKnownToBeOpaqueInRect(toLayoutBox(layer->layoutObject())->paddingBoxRect());
     if (mode == PaintLayerScrollableArea::ConsiderLCDText
         && !layer->compositor()->preferCompositingToLCDTextEnabled()
         && !backgroundSupportsLCDText)
         return false;
 
     // TODO(schenney) Tests fail if we do not also exclude layer->layoutObject()->style()->hasBorderDecoration()
     // (missing background behind dashed borders). Resolve this case, or not, and update this check with
     // the results.
     return !(layer->size().isEmpty()
@@ skipping 257 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollPositionClampScope::clampScrollableAreas()
 {
     for (auto& scrollableArea : *s_needsClamp)
         scrollableArea->clampScrollPositionsAfterLayout();
     delete s_needsClamp;
     s_needsClamp = nullptr;
 }
 
 } // namespace blink