[LayoutNG] Remove unnecessary #inclusions of LayoutObject and derived class definitions.

third_party/WebKit/Source/core/layout/ng/ng_constraint_space.h

 // 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.
 
 #ifndef NGConstraintSpace_h
 #define NGConstraintSpace_h
 
 #include "core/CoreExport.h"
-#include "core/layout/LayoutBox.h"
 #include "core/layout/ng/ng_physical_constraint_space.h"
 #include "core/layout/ng/ng_writing_mode.h"
 #include "platform/heap/Handle.h"
 #include "wtf/text/WTFString.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class LayoutBox;
 class NGFragment;
@@ skipping 100 matching lines @@
 };
 
 inline std::ostream& operator<<(std::ostream& stream,
                                 const NGConstraintSpace& value) {
   return stream << value.toString();
 }
 
 }  // namespace blink
 
 #endif  // NGConstraintSpace_h