Move sticky position constraints update to the pre-paint tree walk.

third_party/WebKit/Source/core/paint/PaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 1018 matching lines @@
     if (curr->isPaintInvalidationContainer())
       return curr;
   }
 
   return nullptr;
 }
 
 void PaintLayer::setNeedsCompositingInputsUpdate() {
   setNeedsCompositingInputsUpdateInternal();
 
-  // TODO(chrishtr): This is a bit of a heavy hammer, because not all
+  // TODO(chrishtr): These are a bit of a heavy hammer, because not all
   // things which require compositing inputs update require a descendant-
   // dependent flags udpate. Reduce call sites after SPv2 launch allows
   /// removal of CompositingInputsUpdater.
   markAncestorChainForDescendantDependentFlagsUpdate();
+  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+    // This update is needed in order to re-compute sticky position constraints,
+    // not for any other reason.
+    layoutObject()->setNeedsPaintPropertyUpdate();
+  }
 }
 
 void PaintLayer::setNeedsCompositingInputsUpdateInternal() {
   m_needsAncestorDependentCompositingInputsUpdate = true;
 
   for (PaintLayer* current = this;
        current && !current->m_childNeedsCompositingInputsUpdate;
        current = current->parent())
     current->m_childNeedsCompositingInputsUpdate = true;
 
@@ skipping 2223 matching lines @@
 }
 
 void showLayerTree(const blink::LayoutObject* layoutObject) {
   if (!layoutObject) {
     LOG(INFO) << "Cannot showLayerTree. Root is (nil)";
     return;
   }
   showLayerTree(layoutObject->enclosingLayer());
 }
 #endif