Make NGLayoutOpportunityIterator to support origin_point.

third_party/WebKit/Source/core/layout/ng/ng_units.cc

 // 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.
 
 #include "core/layout/ng/ng_units.h"
 
 #include "core/layout/ng/ng_writing_mode.h"
 
 namespace blink {
 
@@ skipping 70 matching lines @@
       ASSERT_NOT_REACHED();
       return NGPhysicalOffset();
   }
 }
 
 bool NGLogicalOffset::operator==(const NGLogicalOffset& other) const {
   return std::tie(other.inline_offset, other.block_offset) ==
          std::tie(inline_offset, block_offset);
 }
 
+NGLogicalOffset NGLogicalOffset::operator+(const NGLogicalOffset& other) const {
+  NGLogicalOffset result;
+  result.inline_offset = this->inline_offset + other.inline_offset;
+  result.block_offset = this->block_offset + other.block_offset;
+  return result;
+}
+
+NGLogicalOffset& NGLogicalOffset::operator+=(const NGLogicalOffset& other) {
+  *this = *this + other;
+  return *this;
+}
+
 bool NGBoxStrut::IsEmpty() const {
   return *this == NGBoxStrut();
 }
 
 bool NGBoxStrut::operator==(const NGBoxStrut& other) const {
   return std::tie(other.inline_start, other.inline_end, other.block_start,
                   other.block_end) ==
          std::tie(inline_start, inline_end, block_start, block_end);
 }
 
@@ skipping 48 matching lines @@
 
 bool NGMarginStrut::operator==(const NGMarginStrut& other) const {
   return std::tie(other.margin_block_start, other.margin_block_end,
                   other.negative_margin_block_start,
                   other.negative_margin_block_end) ==
          std::tie(margin_block_start, margin_block_end,
                   negative_margin_block_start, negative_margin_block_end);
 }
 
 }  // namespace blink