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

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1214 matching lines @@
 {
     paintInvalidationState.paintingLayer().setNeedsRepaint();
     invalidateDisplayItemClients(reason);
 }
 
 bool LayoutObject::compositedScrollsWithRespectTo(const LayoutBoxModelObject& paintInvalidationContainer) const
 {
     return paintInvalidationContainer.usesCompositedScrolling() && this != &paintInvalidationContainer;
 }
 
+IntSize LayoutObject::scrollAdjustmentForPaintInvalidation(const LayoutBoxModelObject& paintInvalidationContainer) const
+{
+    // Non-composited scrolling should be included in the bounds of scrolled items. Since mapToVisualRectInAncestorSpace does not include
+    // scrolling of the ancestor, we need to add it back in after.
+    if (paintInvalidationContainer.isBox() && !paintInvalidationContainer.usesCompositedScrolling() && this != &paintInvalidationContainer) {
+        const LayoutBox* box = toLayoutBox(&paintInvalidationContainer);
+        if (box->hasOverflowClip())
+            return -box->scrolledContentOffset();
+    }
+    return IntSize();
+}
+
 void LayoutObject::invalidatePaintRectangle(const LayoutRect& dirtyRect) const
 {
     RELEASE_ASSERT(isRooted());
 
     if (dirtyRect.isEmpty())
         return;
 
     if (view()->document().printing())
         return; // Don't invalidate paints if we're printing.
 
     const LayoutBoxModelObject& paintInvalidationContainer = containerForPaintInvalidation();
     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);
-    }
+    dirtyRectOnBacking.move(scrollAdjustmentForPaintInvalidation(paintInvalidationContainer));
 
     invalidatePaintUsingContainer(paintInvalidationContainer, dirtyRectOnBacking, PaintInvalidationRectangle);
 
     slowSetPaintingLayerNeedsRepaint();
     invalidateDisplayItemClients(PaintInvalidationRectangle);
 }
 
 void LayoutObject::invalidateTreeIfNeeded(const PaintInvalidationState& paintInvalidationState)
 {
     ASSERT(!needsLayout());
@@ skipping 70 matching lines @@
 inline void LayoutObject::invalidateSelectionIfNeeded(const LayoutBoxModelObject& paintInvalidationContainer, const PaintInvalidationState& paintInvalidationState, PaintInvalidationReason invalidationReason)
 {
     // Update selection rect when we are doing full invalidation (in case that the object is moved, composite status changed, etc.)
     // or shouldInvalidationSelection is set (in case that the selection itself changed).
     bool fullInvalidation = isFullPaintInvalidationReason(invalidationReason);
     if (!fullInvalidation && !shouldInvalidateSelection())
         return;
 
     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);
-        }
-    }
+    newSelectionRect.move(scrollAdjustmentForPaintInvalidation(paintInvalidationContainer));
 
     setPreviousSelectionRectForPaintInvalidation(newSelectionRect);
 
     // TODO(wangxianzhu): Combine the following two conditions when removing LayoutView::doingFullPaintInvalidation().
     if (!fullInvalidation)
         fullyInvalidatePaint(paintInvalidationContainer, PaintInvalidationSelection, oldSelectionRect, newSelectionRect);
     if (shouldInvalidateSelection())
         invalidateDisplayItemClientsWithPaintInvalidationState(paintInvalidationState, PaintInvalidationSelection);
 }
 
@@ skipping 12 matching lines @@
         return PaintInvalidationNone; // Don't invalidate paints if we're printing.
 
     const LayoutBoxModelObject& paintInvalidationContainer = paintInvalidationState.paintInvalidationContainer();
     ASSERT(paintInvalidationContainer == containerForPaintInvalidation());
 
     const LayoutRect oldBounds = previousPaintInvalidationRect();
     const LayoutPoint oldLocation = RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() ? LayoutPoint() : previousPositionFromPaintInvalidationBacking();
     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);
-    }
+    IntSize adjustment = scrollAdjustmentForPaintInvalidation(paintInvalidationContainer);
+    newLocation.move(adjustment);
+    newBounds.move(adjustment);
 
     setPreviousPaintInvalidationRect(newBounds);
     if (!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled())
         setPreviousPositionFromPaintInvalidationBacking(newLocation);
 
     if (!shouldCheckForPaintInvalidationRegardlessOfPaintInvalidationState() && paintInvalidationState.forcedSubtreeInvalidationRectUpdateWithinContainerOnly()) {
         // We are done updating the paint invalidation rect. No other paint invalidation work to do for this object.
         return PaintInvalidationNone;
     }
 
@@ skipping 2270 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
     }
 }
 
 #endif