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

third_party/WebKit/Source/core/layout/LayoutObjectTest.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/LayoutObject.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/api/LayoutAPIShim.h"
+#include "core/layout/api/LayoutViewItem.h"
 #include "platform/json/JSONValues.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blink {
 
 class LayoutObjectTest : public RenderingTest {
 public:
     LayoutObjectTest()
         : RenderingTest(SingleChildFrameLoaderClient::create()) {}
 protected:
@@ skipping 99 matching lines @@
         "    <div id='overflow-clip-layer' style='height: 100px; overflow: hidden'></div>"
         "  </div>"
         "</div>");
 
     LayoutObject* overflowClipObject = getLayoutObjectByElementId("overflow-clip-layer");
     LayoutBlock* columns = toLayoutBlock(getLayoutObjectByElementId("columns"));
     EXPECT_EQ(columns->layer(), overflowClipObject->paintingLayer());
 }
 
 } // namespace blink