Make NGLayoutOpportunityIterator to support origin_point.

third_party/WebKit/Source/core/layout/ng/ng_units.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 NGUnits_h
 #define NGUnits_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ng/ng_direction.h"
 #include "core/layout/ng/ng_writing_mode.h"
@@ skipping 31 matching lines @@
   // Converts a logical offset to a physical offset. See:
   // https://drafts.csswg.org/css-writing-modes-3/#logical-to-physical
   // @param container_size the size of the rect (typically a fragment).
   // @param inner_size the size of the inner rect (typically a child fragment).
   CORE_EXPORT NGPhysicalOffset
   ConvertToPhysical(NGWritingMode mode,
                     NGDirection direction,
                     NGPhysicalSize container_size,
                     NGPhysicalSize inner_size) const;
   bool operator==(const NGLogicalOffset& other) const;
-};
 
-// Origin (in logical coordinates) for a fragment or inline content.
-struct NGLogicalOrigin {
-  LayoutUnit inline_offset;
-  LayoutUnit block_offset;
-};
+  NGLogicalOffset operator+(const NGLogicalOffset& other) const;
 
-// Leader point (in logical coordinates) for a text fragment.
-struct NGLogicalLeader {
-  LayoutUnit inline_offset;
-  LayoutUnit block_offset;
+  NGLogicalOffset& operator+=(const NGLogicalOffset& other);
 };
 
 // NGPhysicalOffset is the position of a rect (typically a fragment) relative to
 // its parent rect in the physical coordinate system.
 struct NGPhysicalOffset {
   NGPhysicalOffset() {}
   NGPhysicalOffset(LayoutUnit left, LayoutUnit top) : left(left), top(top) {}
 
   LayoutUnit left;
   LayoutUnit top;
@@ skipping 125 matching lines @@
 
 // Struct to represent a simple edge that has start and end.
 struct NGEdge {
   LayoutUnit start;
   LayoutUnit end;
 };
 
 }  // namespace blink
 
 #endif  // NGUnits_h