Don't adjust for scrolling of the ancestor, rather than un-adjusting for it later.

third_party/WebKit/Source/core/layout/LayoutObject.cpp

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index 78d02a87c11a1c59fab1f61efe381b2dd8aebd62..7dc0425c6ed59a1ad417592c8fb51bb7db353984 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -1246,12 +1246,6 @@ void LayoutObject::invalidatePaintRectangle(const LayoutRect& dirtyRect) const
     LayoutRect dirtyRectOnBacking = dirtyRect;
     PaintLayer::mapRectToPaintInvalidationBacking(*this, paintInvalidationContainer, dirtyRectOnBacking);
 
-    // Composited scrolling should not be included in the bounds of composited-scrolled items.
-    if (compositedScrollsWithRespectTo(paintInvalidationContainer)) {
-        LayoutSize inverseOffset(toLayoutBox(&paintInvalidationContainer)->scrolledContentOffset());
-        dirtyRectOnBacking.move(inverseOffset);
-    }
-
     invalidatePaintUsingContainer(paintInvalidationContainer, dirtyRectOnBacking, PaintInvalidationRectangle);
 
     slowSetPaintingLayerNeedsRepaint();
@@ -1341,17 +1335,9 @@ inline void LayoutObject::invalidateSelectionIfNeeded(const LayoutBoxModelObject
 
     LayoutRect oldSelectionRect = previousSelectionRectForPaintInvalidation();
     LayoutRect newSelectionRect = localSelectionRect();
-    if (!newSelectionRect.isEmpty()) {
+    if (!newSelectionRect.isEmpty())
         paintInvalidationState.mapLocalRectToPaintInvalidationBacking(newSelectionRect);
 
-        // Composited scrolling should not be included in the bounds and position tracking, because the graphics layer backing the scroller
-        // does not move on scroll.
-        if (compositedScrollsWithRespectTo(paintInvalidationContainer)) {
-            LayoutSize inverseOffset(toLayoutBox(&paintInvalidationContainer)->scrolledContentOffset());
-            newSelectionRect.move(inverseOffset);
-        }
-    }
-
     setPreviousSelectionRectForPaintInvalidation(newSelectionRect);
 
     // TODO(wangxianzhu): Combine the following two conditions when removing LayoutView::doingFullPaintInvalidation().
@@ -1383,15 +1369,6 @@ PaintInvalidationReason LayoutObject::invalidatePaintIfNeeded(const PaintInvalid
     LayoutRect newBounds = paintInvalidationState.computePaintInvalidationRectInBacking();
     LayoutPoint newLocation = RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() ? LayoutPoint() : paintInvalidationState.computePositionFromPaintInvalidationBacking();
 
-    // Composited scrolling should not be included in the bounds and position tracking, because the graphics layer backing the scroller
-    // does not move on scroll.
-    // TODO(chrishtr): can we just avoid adding in the scroll in the first place in LayoutBox::mapScrollingContentsRectToBoxSpace?
-    if (compositedScrollsWithRespectTo(paintInvalidationContainer)) {
-        LayoutSize inverseOffset(toLayoutBox(&paintInvalidationContainer)->scrolledContentOffset());
-        newLocation.move(inverseOffset);
-        newBounds.move(inverseOffset);
-    }
-
     setPreviousPaintInvalidationRect(newBounds);
     if (!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled())
         setPreviousPositionFromPaintInvalidationBacking(newLocation);