Correct for enclosing layers scroll position in sticky_data->main_thread_offset

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 273 matching lines @@
   m_graphicsLayer->setFilters(
       owningLayer().createCompositorFilterOperationsForFilter(style));
 }
 
 void CompositedLayerMapping::updateBackdropFilters(const ComputedStyle& style) {
   m_graphicsLayer->setBackdropFilters(
       owningLayer().createCompositorFilterOperationsForBackdropFilter(style));
 }
 
 void CompositedLayerMapping::updateStickyConstraints(
-    const ComputedStyle& style) {
+    const ComputedStyle& style,
+    const PaintLayer* compositingContainer) {
   bool sticky = style.position() == EPosition::kSticky;
   const PaintLayer* ancestorOverflowLayer =
       m_owningLayer.ancestorOverflowLayer();
   // TODO(flackr): Do we still need this?
   if (sticky) {
     if (!ancestorOverflowLayer->isRootLayer()) {
       sticky = ancestorOverflowLayer->needsCompositedScrolling();
     } else {
       sticky = layoutObject().view()->frameView()->isScrollable();
     }
   }
 
   WebLayerStickyPositionConstraint webConstraint;
   if (sticky) {
     const StickyPositionScrollingConstraints& constraints =
         ancestorOverflowLayer->getScrollableArea()->stickyConstraintsMap().at(
             &m_owningLayer);
 
-    // Find the layout offset of the unshifted sticky box within its enclosing
-    // layer.
+    // Find the layout offset of the unshifted sticky box within its
+    // compositingContainer. If the enclosing layer is not the scroller, then
+    // the offset must be adjusted to include the scroll offset to keep it
+    // relative to compositingContainer.
     LayoutPoint enclosingLayerOffset;
-    m_owningLayer.enclosingLayerWithCompositedLayerMapping(ExcludeSelf)
-        ->convertToLayerCoords(m_owningLayer.ancestorOverflowLayer(),
-                               enclosingLayerOffset);
+    compositingContainer->convertToLayerCoords(ancestorOverflowLayer,
+                                               enclosingLayerOffset);
+    if (compositingContainer != ancestorOverflowLayer) {
+      enclosingLayerOffset += LayoutSize(
+          ancestorOverflowLayer->getScrollableArea()->getScrollOffset());
+    }
+
     FloatPoint stickyBoxOffset =
         constraints.scrollContainerRelativeStickyBoxRect().location();
     DCHECK(!m_contentOffsetInCompositingLayerDirty);
     stickyBoxOffset.moveBy(FloatPoint(-enclosingLayerOffset) -
                            FloatSize(contentOffsetInCompositingLayer()));
 
     webConstraint.isSticky = true;
     webConstraint.isAnchoredLeft =
         constraints.anchorEdges() &
         StickyPositionScrollingConstraints::AnchorEdgeLeft;
@@ skipping 678 matching lines @@
   FloatSize contentsSize(relativeCompositingBounds.size());
 
   updateMainGraphicsLayerGeometry(relativeCompositingBounds,
                                   localCompositingBounds,
                                   graphicsLayerParentLocation);
   updateOverflowControlsHostLayerGeometry(compositingStackingContext,
                                           compositingContainer,
                                           graphicsLayerParentLocation);
   updateContentsOffsetInCompositingLayer(snappedOffsetFromCompositedAncestor,
                                          graphicsLayerParentLocation);
-  updateStickyConstraints(layoutObject().styleRef());
+  updateStickyConstraints(layoutObject().styleRef(), compositingContainer);
   updateSquashingLayerGeometry(
       graphicsLayerParentLocation, compositingContainer, m_squashedLayers,
       m_squashingLayer.get(), &m_squashingLayerOffsetFromTransformedAncestor,
       layersNeedingPaintInvalidation);
 
   // If we have a layer that clips children, position it.
   IntRect clippingBox;
   if (m_childContainmentLayer && layoutObject().isBox())
     clippingBox = clipBox(toLayoutBox(layoutObject()));
 
@@ skipping 2453 matching lines @@
   } else if (graphicsLayer == m_decorationOutlineLayer.get()) {
     name = "Decoration Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink