Have LayoutObject::decoratedName() decorate for multicol spanners.

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 1078 matching lines @@
     name.append(this->name());
 
     if (isAnonymous())
         name.append(" (anonymous)");
     if (isOutOfFlowPositioned())
         name.append(" (positioned)");
     if (isRelPositioned())
         name.append(" (relative positioned)");
     if (isFloating())
         name.append(" (floating)");
+    if (spannerPlaceholder())
+        name.append(" (column spanner)");
 
     return name.toString();
 }
 
 String LayoutObject::debugName() const
 {
     StringBuilder name;
     name.append(decoratedName());
 
     if (const Node* node = this->node()) {
@@ skipping 2198 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