Implement PaintLayer::scrollsWithViewport for SPv2.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 655 matching lines @@
                         UseTransforms | TraverseDocumentBoundaries)
                     .boundingBox());
           } else {
             parentBox = nullptr;
           }
         }
       }
     }
   }
 
-  // If we are fixed-position and scroll with the viewport, it is useless to
+  // If we are fixed-position and stick to the viewport, it is useless to
   // scroll the parent.
-  if (style()->position() == FixedPosition && hasLayer() &&
-      layer()->scrollsWithViewport()) {
+  if (style()->position() == FixedPosition &&
+      containerForFixedPosition() == view()) {

[chrishtr, 2016/12/07 18:07:19]

This one was pretty easy to adjust to not call sticksToViewport, so I just
changed it. This method is called during layout, so it's not ok to update
all lifecycle phases.

     return;
   }
 
   if (frame()->page()->autoscrollController().autoscrollInProgress())
     parentBox = enclosingScrollableBox();
 
   if (parentBox)
     parentBox->scrollRectToVisible(newRect, alignX, alignY, scrollType,
                                    makeVisibleInVisualViewport);
 }
@@ skipping 330 matching lines @@
 
   return windowAutoscrollPoint - pointInRootFrame;
 }
 
 LayoutBox* LayoutBox::findAutoscrollable(LayoutObject* layoutObject) {
   while (
       layoutObject &&
       !(layoutObject->isBox() && toLayoutBox(layoutObject)->canAutoscroll())) {
     // Do not start autoscroll when the node is inside a fixed-position element.
     if (layoutObject->isBox() && toLayoutBox(layoutObject)->hasLayer() &&
-        toLayoutBox(layoutObject)->layer()->scrollsWithViewport()) {
+        toLayoutBox(layoutObject)->layer()->sticksToViewport()) {
       return nullptr;
     }
 
     if (!layoutObject->parent() &&
         layoutObject->node() == layoutObject->document() &&
         layoutObject->document().localOwner())
       layoutObject = layoutObject->document().localOwner()->layoutObject();
     else
       layoutObject = layoutObject->parent();
   }
@@ skipping 4582 matching lines @@
   LayoutRect rect = frameRect();
 
   LayoutBlock* block = containingBlock();
   if (block)
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 }  // namespace blink