Don't include LayoutObject-derived headers where not needed.

third_party/WebKit/Source/core/editing/EditingUtilities.cpp

 /*
  * Copyright (C) 2004, 2005, 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 38 matching lines @@
 #include "core/frame/LocalFrame.h"
 #include "core/frame/UseCounter.h"
 #include "core/html/HTMLBRElement.h"
 #include "core/html/HTMLDivElement.h"
 #include "core/html/HTMLLIElement.h"
 #include "core/html/HTMLParagraphElement.h"
 #include "core/html/HTMLSpanElement.h"
 #include "core/html/HTMLTableCellElement.h"
 #include "core/html/HTMLUListElement.h"
 #include "core/layout/LayoutObject.h"
-#include "core/layout/LayoutTableCell.h"
 #include "wtf/Assertions.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/text/StringBuilder.h"
 #include "wtf/text/Unicode.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 namespace {
@@ skipping 1424 matching lines @@
   if (layoutObject->isBR()) {
     layoutObject = layoutObject->parent();
     if (!layoutObject)
       return false;
   }
   if (!layoutObject->isTableCell())
     return false;
 
   // Check that the table cell contains no child layoutObjects except for
   // perhaps a single <br>.
-  LayoutObject* childLayoutObject =
-      toLayoutTableCell(layoutObject)->firstChild();
+  LayoutObject* childLayoutObject = layoutObject->slowFirstChild();
   if (!childLayoutObject)
     return true;
   if (!childLayoutObject->isBR())
     return false;
   return !childLayoutObject->nextSibling();
 }
 
 HTMLElement* createDefaultParagraphElement(Document& document) {
   switch (document.frame()->editor().defaultParagraphSeparator()) {
     case EditorParagraphSeparatorIsDiv:
@@ skipping 591 matching lines @@
         return InputType::DeleteWordBackward;
       if (granularity == LineBoundary)
         return InputType::DeleteLineBackward;
       return InputType::DeleteContentBackward;
     default:
       return InputType::None;
   }
 }
 
 }  // namespace blink