Include scroll offset in scrolling contents painted background rect invalidation.

third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp

Index: third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
index 81a301b5097852b9f51aed67aee644a216f7b286..3a7102b30e63b5ca5462b35bb4b1ae86a1f47bfa 100644
--- a/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
+++ b/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
@@ -228,7 +228,9 @@ void ObjectPaintInvalidator::setBackingNeedsPaintInvalidationInRect(const Layout
         if (layer.compositedLayerMapping()->backgroundPaintsOntoScrollingContentsLayer()) {
             // TODO(flackr): Get a correct rect in the context of the scrolling contents layer to update
             // rather than updating the entire rect.
-            const LayoutRect& scrollingContentsRect = toLayoutBox(m_object).layoutOverflowRect();
+            const LayoutBox& box = toLayoutBox(m_object);
+            LayoutRect scrollingContentsRect = box.layoutOverflowRect();
+            scrollingContentsRect.move(-box.scrolledContentOffset());
             layer.compositedLayerMapping()->setScrollingContentsNeedDisplayInRect(scrollingContentsRect, reason, m_object);
             layer.setNeedsRepaint();
             invalidateDisplayItemClient(*layer.compositedLayerMapping()->scrollingContentsLayer(), reason);