Create LineLayout api

Source/core/layout/api/LineLayoutBox.h

Index: Source/core/layout/api/LineLayoutBox.h
diff --git a/Source/core/layout/api/LineLayoutBox.h b/Source/core/layout/api/LineLayoutBox.h
new file mode 100644
index 0000000000000000000000000000000000000000..c6e71824066c65ea62ff2a67bcaf95acdc3b8bc9
--- /dev/null
+++ b/Source/core/layout/api/LineLayoutBox.h
@@ -0,0 +1,55 @@
+// 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/LayoutBox.h"
+#include "core/layout/api/LineLayoutItem.h"
+#include "platform/LayoutUnit.h"
+
+namespace blink {
+
+class LayoutBox;
+
+class LineLayoutBox : public LineLayoutItem {
+public:
+    LineLayoutBox(LayoutBox* layoutBox)
+        : LineLayoutItem(layoutBox)
+    {
+    }
+
+    LineLayoutBox(const LineLayoutItem& item)
+        : LineLayoutItem(item)
+    {
+        ASSERT(!item.hasLayoutObject() || item.isBox());
+    }
+
+    LineLayoutBox() { }
+
+    void setLogicalHeight(LayoutUnit size)
+    {
+        toBox()->setLogicalHeight(size);
+    }
+
+    LayoutUnit logicalHeight() const
+    {
+        return toBox()->logicalHeight();
+    }
+
+private:
+    LayoutBox* toBox()
+    {
+        return toLayoutBox(layoutObject());
+    }
+
+    const LayoutBox* toBox() const
+    {
+        return toLayoutBox(layoutObject());
+    }
+};
+
+} // namespace blink
+
+#endif // LineLayoutBox_h