[layoutng] Margin support, part 1

third_party/WebKit/Source/core/layout/ng/ng_margin_strut.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 NGMarginStrut_h
 #define NGMarginStrut_h
 
 #include "core/CoreExport.h"
 #include "platform/LayoutUnit.h"
 
 namespace blink {
 
+// Stores the four margins of a box
+struct NGBoxMargins {
+  LayoutUnit inlineStart;
+  LayoutUnit inlineEnd;
+  LayoutUnit blockStart;
+  LayoutUnit blockEnd;
+
+  LayoutUnit inlineSum() const { return inlineStart + inlineEnd; }
+  LayoutUnit blockSum() const { return blockStart + blockEnd; }
+};
+
 // This struct is used for the margin collapsing calculation.
 struct NGMarginStrut {
   LayoutUnit marginBlockStart;
   LayoutUnit marginBlockEnd;
 
   LayoutUnit negativeMarginBlockStart;
   LayoutUnit negativeMarginBlockEnd;
 };
 
 }  // namespace blink
 
 #endif  // NGMarginStrut_h