Implement PaintLayer::scrollsWithViewport for SPv2.

third_party/WebKit/Source/core/page/AutoscrollController.cpp

Index: third_party/WebKit/Source/core/page/AutoscrollController.cpp
diff --git a/third_party/WebKit/Source/core/page/AutoscrollController.cpp b/third_party/WebKit/Source/core/page/AutoscrollController.cpp
index 32b5c3823ab7dce1a1a6944d0f9a59bd400e1a0e..c907c940f95f35e40d0b8759049a26fd19e00701 100644
--- a/third_party/WebKit/Source/core/page/AutoscrollController.cpp
+++ b/third_party/WebKit/Source/core/page/AutoscrollController.cpp
@@ -77,6 +77,8 @@ void AutoscrollController::startAutoscrollForSelection(
   // it's already active.
   if (m_autoscrollType != NoAutoscroll)
     return;
+  if (layoutObject)
+    layoutObject->frameView()->updateAllLifecyclePhasesExceptPaint();
   LayoutBox* scrollable = LayoutBox::findAutoscrollable(layoutObject);
   if (!scrollable)
     scrollable =
@@ -163,6 +165,10 @@ void AutoscrollController::updateDragAndDrop(Node* dropTargetNode,
           dropTargetNode->layoutObject()->frame())
     return;
 
+  dropTargetNode->layoutObject()
+      ->frameView()
+      ->updateAllLifecyclePhasesExceptPaint();
+
   LayoutBox* scrollable =
       LayoutBox::findAutoscrollable(dropTargetNode->layoutObject());
   if (!scrollable) {