Implement PaintLayer::scrollsWithViewport for SPv2.

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index a089203f9ba2198a3b73b6b5029e8b9054a83fe6..e37f85862a863e57c23f8d5883134cbf871ecd2b 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -2874,8 +2874,11 @@ void FrameView::updateLifecyclePhasesInternal(
       if (targetState >= DocumentLifecycle::PrePaintClean) {
         if (!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled())
           invalidateTreeIfNeededRecursive();
-        if (view.compositor()->inCompositingMode())
-          scrollingCoordinator()->updateAfterCompositingChangeIfNeeded();
+
+        if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+          if (view.compositor()->inCompositingMode())
+            scrollingCoordinator()->updateAfterCompositingChangeIfNeeded();
+        }
 
         updateCompositedSelectionIfNeeded();
       }