Fix sticky constraints and update sticky layer positions recursively after scroll.

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

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1591 matching lines @@
     if (m_frame->document() && !m_frame->document()->layoutViewItem().isNull())
         m_frame->document()->fetcher()->updateAllImageResourcePriorities();
 }
 
 void FrameView::updateLayersAndCompositingAfterScrollIfNeeded()
 {
     // Nothing to do after scrolling if there are no fixed position elements.
     if (!hasViewportConstrainedObjects())
         return;
 
-    // Update sticky position objects which are stuck to the viewport.
+    // Mark sticky position objects which are stuck to the viewport for positioned movement.
     for (const auto& viewportConstrainedObject : *m_viewportConstrainedObjects) {
         LayoutObject* layoutObject = viewportConstrainedObject;
-        PaintLayer* layer = toLayoutBoxModelObject(layoutObject)->layer();
         if (layoutObject->style()->position() == StickyPosition)
-            layer->updateLayerPosition();
+            layoutObject->setNeedsPositionedMovementLayout();

[chrishtr, 2016/05/31 20:19:53]

What about sticky objects that are not stuck to the viewport?

[flackr, 2016/05/31 20:38:52]

This is already handled by PaintLayerScrollableArea::setScrollOffset calling
updateLayerPositionsAfterOverflowScroll which is used for overflow scrollers.
It's probably best to be consistent with that so I'll use this update method. It
updates the layer positions recursively as needed though does require the same
compositing assert disabler used there:

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

Should I add a second test for an overflow scroller?

     }
 
     // If there fixed position elements, scrolling may cause compositing layers to change.
     // Update widget and layer positions after scrolling, but only if we're not inside of
     // layout.
     if (!m_nestedLayoutCount) {
         updateWidgetGeometries();
         LayoutViewItem layoutViewItem = this->layoutViewItem();
         if (!layoutViewItem.isNull())
             layoutViewItem.layer()->setNeedsCompositingInputsUpdate();
@@ skipping 2487 matching lines @@
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 LayoutBox& FrameView::boxForScrollControlPaintInvalidation() const
 {
     ASSERT(!layoutViewItem().isNull());
     return *layoutView();
 }
 
 } // namespace blink