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

third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.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/PaintLayerScrollableArea.h"
 
 #include "core/frame/FrameView.h"
-#include "core/layout/LayoutBlock.h"
+#include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/paint/PaintLayer.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
 
 namespace blink {
 
 class PaintLayerScrollableAreaTest : public RenderingTest {
  public:
   PaintLayerScrollableAreaTest()
       : RenderingTest(SingleChildFrameLoaderClient::create()) {}
 
   bool canPaintBackgroundOntoScrollingContentsLayer(const char* elementId) {
     PaintLayer* paintLayer =
-        toLayoutBlock(getLayoutObjectByElementId(elementId))->layer();
+        toLayoutBoxModelObject(getLayoutObjectByElementId(elementId))->layer();
     return paintLayer->canPaintBackgroundOntoScrollingContentsLayer();
   }
 
  private:
   void SetUp() override {
     RenderingTest::SetUp();
     enableCompositing();
   }
 };
 
@@ skipping 365 matching lines @@
   ASSERT_TRUE(blackLayer);
 
   ASSERT_EQ(ScrollbarOverlayColorTheme::ScrollbarOverlayColorThemeDark,
             noneLayer->getScrollableArea()->getScrollbarOverlayColorTheme());
   ASSERT_EQ(ScrollbarOverlayColorTheme::ScrollbarOverlayColorThemeDark,
             whiteLayer->getScrollableArea()->getScrollbarOverlayColorTheme());
   ASSERT_EQ(ScrollbarOverlayColorTheme::ScrollbarOverlayColorThemeLight,
             blackLayer->getScrollableArea()->getScrollbarOverlayColorTheme());
 }
 }