Create LineLayout api

Source/core/layout/api/LineLayoutBox.h

+// 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.
+
+#ifndef LineLayoutBox_h
+#define LineLayoutBox_h
+
+#include "core/layout/api/LineLayoutItem.h"
+#include "platform/LayoutUnit.h"
+
+namespace blink {
+
+class LayoutBox;
+
+class LineLayoutBox : public LineLayoutItem {
+public:
+    LineLayoutBox(LayoutBox*);
+    LineLayoutBox(const LineLayoutItem&);
+    LineLayoutBox() { }
+
+    void setLogicalHeight(LayoutUnit size);
+    LayoutUnit logicalHeight() const;
+
+private:
+    LayoutBox* box();
+    const LayoutBox* box() const;
+};
+
+} // namespace blink
+
+#endif // LineLayoutBox_h