Use invalidation sets for :-webkit-drag.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 2667 matching lines @@
 {
     return createPositionWithAffinity(caretMinOffset());
 }
 
 void LayoutObject::updateDragState(bool dragOn)
 {
     bool valueChanged = (dragOn != isDragging());
     setIsDragging(dragOn);
     if (valueChanged && node()) {
         if (node()->isElementNode() && toElement(node())->childrenOrSiblingsAffectedByDrag())
-            node()->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::Drag));
+            document().styleEngine().pseudoStateChangedForElement(CSSSelector::PseudoDrag, *toElement(node()));
         else if (style()->affectedByDrag())
             node()->setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::Drag));
     }
     for (LayoutObject* curr = slowFirstChild(); curr; curr = curr->nextSibling())
         curr->updateDragState(dragOn);
 }
 
 CompositingState LayoutObject::compositingState() const
 {
     return hasLayer() ? toLayoutBoxModelObject(this)->layer()->compositingState() : NotComposited;
@@ skipping 819 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif