LayoutView's paint layer should clip to the full viewport size.

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

Index: third_party/WebKit/Source/core/layout/LayoutView.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutView.cpp b/third_party/WebKit/Source/core/layout/LayoutView.cpp
index bc3ab68c3224a822d95c125fd48b2e22d2e619da..f211a982b81cdf218b5e0441a5a251c52b194d3a 100644
--- a/third_party/WebKit/Source/core/layout/LayoutView.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutView.cpp
@@ -307,7 +307,9 @@ LayoutRect LayoutView::localVisualRect() const {
   // TODO(wangxianzhu): This is only required without rootLayerScrolls (though
   // it is also correct but unnecessary with rootLayerScrolls) because of the
   // special LayoutView overflow model.
-  return visualOverflowRect();
+  LayoutRect rect = visualOverflowRect();
+  rect.unite(LayoutRect(rect.location(), viewRect().size()));
+  return rect;
 }
 
 void LayoutView::mapLocalToAncestor(const LayoutBoxModelObject* ancestor,