Repaint non-stacking-context composited children when they scroll.

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 365 matching lines @@
 
     FloatQuad quadForFakeMouseMoveEvent = FloatQuad(FloatRect(layer()->layoutObject()->previousPaintInvalidationRectIncludingCompositedScrolling(paintInvalidationContainer)));
 
     quadForFakeMouseMoveEvent = paintInvalidationContainer.localToAbsoluteQuad(quadForFakeMouseMoveEvent);
     frame->eventHandler().dispatchFakeMouseMoveEventSoonInQuad(quadForFakeMouseMoveEvent);
 
     bool requiresPaintInvalidation = true;
 
     if (box().view()->compositor()->inCompositingMode()) {
         bool onlyScrolledCompositedLayers = scrollsOverflow()
-            && !layer()->hasVisibleNonLayerContent()
-            && !layer()->hasNonCompositedChild()
+            && layer()->isAllScrollingContentComposited()
             && box().style()->backgroundLayers().attachment() != LocalBackgroundAttachment;
 
         if (usesCompositedScrolling() || onlyScrolledCompositedLayers)
             requiresPaintInvalidation = false;
     }
 
     // Only the root layer can overlap non-composited fixed-position elements.
     if (!requiresPaintInvalidation && layer()->isRootLayer() && frameView->hasViewportConstrainedObjects()) {
         if (!frameView->invalidateViewportConstrainedObjects())
             requiresPaintInvalidation = true;
@@ skipping 1339 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollPositionClampScope::clampScrollableAreas()
 {
     for (auto& scrollableArea : *s_needsClamp)
         scrollableArea->clampScrollPositionsAfterLayout();
     delete s_needsClamp;
     s_needsClamp = nullptr;
 }
 
 } // namespace blink