[layoutng] Move and rename NGBoxMargins to NGBoxStrut

third_party/WebKit/Source/core/layout/ng/ng_units.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 NGUnits_h
 #define NGUnits_h
 
 #include "platform/LayoutUnit.h"
 
 namespace blink {
@@ skipping 29 matching lines @@
   NGPhysicalLocation location;
 };
 
 struct NGPixelSnappedPhysicalRect {
   int top;
   int left;
   int width;
   int height;
 };
 
+// This struct is used for storing margins, borders or padding of a box on all
+// four edges.
+struct NGBoxStrut {
+  LayoutUnit inline_start;
+  LayoutUnit inline_end;
+  LayoutUnit block_start;
+  LayoutUnit block_end;
+
+  LayoutUnit InlineSum() const { return inline_start + inline_end; }
+  LayoutUnit BlockSum() const { return block_start + block_end; }
+};
+
 }  // namespace blink
 
 #endif  // NGUnits_h