[LayoutNG] Initial support for multicol, introducing NGBlockBreakToken.

third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.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_fragment_builder.h"
 
 #include "core/layout/ng/ng_block_node.h"
+#include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_fragment.h"
 #include "core/layout/ng/ng_physical_box_fragment.h"
 #include "core/layout/ng/ng_physical_text_fragment.h"
 
 namespace blink {
 
 NGFragmentBuilder::NGFragmentBuilder(NGPhysicalFragment::NGFragmentType type)
     : type_(type),
       writing_mode_(kHorizontalTopBottom),
       direction_(TextDirection::kLtr) {}
@@ skipping 111 matching lines @@
   margin_strut_.margin_block_end = from.margin_block_end;
   margin_strut_.negative_margin_block_end = from.negative_margin_block_end;
   return *this;
 }
 
 NGPhysicalBoxFragment* NGFragmentBuilder::ToBoxFragment() {
   // TODO(layout-ng): Support text fragments
   DCHECK_EQ(type_, NGPhysicalFragment::kFragmentBox);
   DCHECK_EQ(offsets_.size(), children_.size());
 
+  auto* break_token = break_token_.get();
+  break_token_ = nullptr;
+
   NGPhysicalSize physical_size = size_.ConvertToPhysical(writing_mode_);
   HeapVector<Member<const NGPhysicalFragment>> children;
   children.reserveCapacity(children_.size());
 
   for (size_t i = 0; i < children_.size(); ++i) {
     NGPhysicalFragment* child = children_[i].get();
     child->SetOffset(offsets_[i].ConvertToPhysical(
         writing_mode_, direction_, physical_size, child->Size()));
     children.push_back(child);
   }
   return new NGPhysicalBoxFragment(
       physical_size, overflow_.ConvertToPhysical(writing_mode_), children,
-      out_of_flow_descendants_, out_of_flow_positions_, margin_strut_);
+      out_of_flow_descendants_, out_of_flow_positions_, margin_strut_,
+      break_token);
 }
 
 NGPhysicalTextFragment* NGFragmentBuilder::ToTextFragment(NGInlineNode* node,
                                                           unsigned start_index,
                                                           unsigned end_index) {
   DCHECK_EQ(type_, NGPhysicalFragment::kFragmentText);
   DCHECK(children_.isEmpty());
   DCHECK(offsets_.isEmpty());
   return new NGPhysicalTextFragment(
       node, start_index, end_index, size_.ConvertToPhysical(writing_mode_),
       overflow_.ConvertToPhysical(writing_mode_), out_of_flow_descendants_,
       out_of_flow_positions_);
 }
 
 DEFINE_TRACE(NGFragmentBuilder) {
   visitor->trace(children_);
   visitor->trace(out_of_flow_descendant_candidates_);
   visitor->trace(out_of_flow_descendants_);
+  visitor->trace(break_token_);
 }
 
 }  // namespace blink