Don't include headers from the layout API from other headers needlessly.

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

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 25 matching lines @@
 #include "core/html/HTMLElement.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/LayoutDetailsMarker.h"
 #include "core/layout/LayoutFileUploadControl.h"
 #include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutListItem.h"
 #include "core/layout/LayoutListMarker.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutTableCell.h"
 #include "core/layout/LayoutView.h"
+#include "core/layout/api/LayoutViewItem.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/layout/line/InlineTextBox.h"
 #include "core/layout/svg/LayoutSVGGradientStop.h"
 #include "core/layout/svg/LayoutSVGImage.h"
 #include "core/layout/svg/LayoutSVGInlineText.h"
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/layout/svg/LayoutSVGShape.h"
 #include "core/layout/svg/LayoutSVGText.h"
 #include "core/layout/svg/SVGLayoutTreeAsText.h"
 #include "core/page/PrintContext.h"
@@ skipping 788 matching lines @@
     element->document().updateStyleAndLayout();
 
     LayoutObject* layoutObject = element->layoutObject();
     if (!layoutObject || !layoutObject->isListItem())
         return String();
 
     return toLayoutListItem(layoutObject)->markerText();
 }
 
 } // namespace blink