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

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

 // Copyright 2015 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/layout/ScrollAnchor.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/UseCounter.h"
+#include "core/layout/LayoutBlockFlow.h"
+#include "core/layout/api/LayoutBoxItem.h"
 #include "core/layout/line/InlineTextBox.h"
 #include "core/paint/PaintLayerScrollableArea.h"
 #include "platform/Histogram.h"
 
 namespace blink {
 
 using Corner = ScrollAnchor::Corner;
 
 ScrollAnchor::ScrollAnchor()
     : m_anchorObject(nullptr)
@@ skipping 268 matching lines @@
     return m_anchorObject == layoutObject;
 }
 
 void ScrollAnchor::notifyRemoved(LayoutObject* layoutObject)
 {
     if (m_anchorObject == layoutObject)
         clear();
 }
 
 } // namespace blink