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

third_party/WebKit/Source/core/paint/PaintPropertyTreePrinter.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/paint/PaintPropertyTreePrinter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
+#include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/ObjectPaintProperties.h"
 
 #include <iomanip>
 #include <sstream>
 
 #ifndef NDEBUG
 
 namespace blink {
 namespace {
@@ skipping 454 matching lines @@
 
 String paintPropertyTreeGraph(const blink::FrameView& frameView)
 {
     blink::PaintPropertyTreeGraphBuilder builder;
     StringBuilder stringBuilder;
     builder.generateTreeGraph(frameView, stringBuilder);
     return stringBuilder.toString();
 }
 
 #endif