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

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 15 matching lines @@
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutGeometryMap.h"
 #include "core/layout/LayoutMedia.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/ViewFragmentationContext.h"
 #include "core/layout/api/LayoutAPIShim.h"
+#include "core/layout/api/LayoutPartItem.h"
+#include "core/layout/api/LayoutViewItem.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
 #include "core/page/Page.h"
 #include "core/paint/PaintLayer.h"
 #include "core/paint/ViewPainter.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "platform/Histogram.h"
 #include "platform/TraceEvent.h"
 #include "platform/TracedValue.h"
 #include "platform/geometry/FloatQuad.h"
 #include "platform/geometry/TransformState.h"
@@ skipping 944 matching lines @@
     // of this override. All frame scrolling should be handled by
     // ViewportScrollCallback.
 
     if (!frameView())
         return ScrollResult(false, false, delta.width(), delta.height());
 
     return frameView()->getScrollableArea()->userScroll(granularity, delta);
 }
 
 } // namespace blink