Implement relative utilities

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

Index: third_party/WebKit/Source/core/layout/ng/ng_relative_utils.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_relative_utils.h b/third_party/WebKit/Source/core/layout/ng/ng_relative_utils.h
new file mode 100644
index 0000000000000000000000000000000000000000..80e0a80a14b6409bc90445c54951b192a6ffc23a
--- /dev/null
+++ b/third_party/WebKit/Source/core/layout/ng/ng_relative_utils.h
@@ -0,0 +1,28 @@
+// Copyright 2017 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 NGRelativeUtils_h
+#define NGRelativeUtils_h
+
+#include "core/CoreExport.h"
+#include "core/layout/ng/geometry/ng_logical_size.h"
+#include "platform/text/TextDirection.h"
+
+namespace blink {
+
+class ComputedStyle;
+struct NGLogicalOffset;
+
+// Implements relative positioning spec:
+// https://www.w3.org/TR/css-position-3/#rel-pos
+// Return relative position offset as defined by style.
+CORE_EXPORT NGLogicalOffset
+ComputeRelativeOffset(const ComputedStyle& child_style,
+                      NGWritingMode container_writing_mode,
+                      TextDirection container_direction,
+                      NGLogicalSize container_size);
+
+}  // namespace blink
+
+#endif  // NGRelativeUtils_h