[LayoutNG] Introduce NGPositionedFloat.

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

+// 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 NGPositionedFloat_h
+#define NGPositionedFloat_h
+
+#include "core/CoreExport.h"
+#include "core/layout/ng/ng_physical_fragment.h"
+
+namespace blink {
+
+// Contains the information necessary for copying back data to a FloatingObject.
+struct CORE_EXPORT NGPositionedFloat {
+  NGPositionedFloat(RefPtr<NGPhysicalFragment> fragment,
+                    NGLogicalOffset offset,
+                    LayoutUnit left_offset)
+      : fragment(fragment), offset(offset), left_offset(left_offset) {}
+
+  RefPtr<NGPhysicalFragment> fragment;
+  NGLogicalOffset offset;
+
+  // In the case where a legacy FloatingObject is attached to not its own
+  // parent, e.g. a float surrounded by a bunch of nested empty divs,
+  // NG float fragment's LeftOffset() cannot be used as legacy FloatingObject's
+  // left offset because that offset should be relative to the original float
+  // parent.
+  // {@code left_offset} is calculated when we know to which parent this float
+  // would be attached.
+  LayoutUnit left_offset;
+};
+
+}  // namespace blink
+
+#endif  // NGPositionedFloat_h