Update drag images to paint from the nearest self painting layer

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>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 2434 matching lines @@
     bool isSelfPaintingLayer = shouldBeSelfPaintingLayer();
     if (this->isSelfPaintingLayer() == isSelfPaintingLayer)
         return;
 
     m_isSelfPaintingLayer = isSelfPaintingLayer;
 
     if (parent())
         parent()->dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 }
 
+PaintLayer* PaintLayer::enclosingSelfPaintingLayer()
+{
+    PaintLayer* layer = this;
+    while (layer && !layer->isSelfPaintingLayer())
+        layer = layer->parent();
+    return layer;
+}
+
 bool PaintLayer::hasNonEmptyChildLayoutObjects() const
 {
     // Some HTML can cause whitespace text nodes to have layoutObjects, like:
     // <div>
     // <img src=...>
     // </div>
     // so test for 0x0 LayoutTexts here
     for (LayoutObject* child = layoutObject()->slowFirstChild(); child; child = child->nextSibling()) {
         if (!child->hasLayer()) {
             if (child->isLayoutInline() || !child->isBox())
@@ skipping 363 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif