[LayoutNG] Initial support for multicol, introducing NGBlockBreakToken.

third_party/WebKit/Source/core/layout/ng/ng_block_node.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_block_node.h"
 
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/api/LineLayoutAPIShim.h"
 #include "core/layout/line/InlineIterator.h"
 #include "core/layout/ng/layout_ng_block_flow.h"
@@ skipping 185 matching lines @@
 }
 
 void NGBlockNode::SetNextSibling(NGBlockNode* sibling) {
   next_sibling_ = sibling;
 }
 
 void NGBlockNode::SetFirstChild(NGLayoutInputNode* child) {
   first_child_ = child;
 }
 
+NGBreakToken* NGBlockNode::CurrentBreakToken() const {
+  return fragment_ ? fragment_->BreakToken() : nullptr;
+}
+
 DEFINE_TRACE(NGBlockNode) {
   visitor->trace(layout_coordinator_);
   visitor->trace(minmax_algorithm_);
   visitor->trace(fragment_);
   visitor->trace(next_sibling_);
   visitor->trace(first_child_);
   NGLayoutInputNode::trace(visitor);
 }
 
 void NGBlockNode::PositionUpdated() {
@@ skipping 120 matching lines @@
   return builder.ToBoxFragment();
 }
 
 void NGBlockNode::UseOldOutOfFlowPositioning() {
   DCHECK(layout_box_);
   DCHECK(layout_box_->isOutOfFlowPositioned());
   layout_box_->containingBlock()->insertPositionedObject(layout_box_);
 }
 
 }  // namespace blink