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

third_party/WebKit/Source/core/observer/ResizeObserverEntry.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/observer/ResizeObserverEntry.h"
 
 #include "core/dom/ClientRect.h"
 #include "core/dom/Element.h"
-#include "core/layout/LayoutBox.h"
 #include "core/observer/ResizeObservation.h"
 
 namespace blink {
 
 ResizeObserverEntry::ResizeObserverEntry(Element* target,
                                          const LayoutRect& contentRect)
     : m_target(target) {
   m_contentRect = ClientRect::create(FloatRect(
       FloatPoint(contentRect.location()), FloatSize(contentRect.size())));
 }
 
 DEFINE_TRACE(ResizeObserverEntry) {
   visitor->trace(m_target);
   visitor->trace(m_contentRect);
 }
 
 }  // namespace blink