[LayoutNG] Allow block-flow layout to be fragmented using new approach.

third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.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/layout_ng_block_flow.h"
 
 #include "core/layout/LayoutAnalyzer.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_fragment.h"
 
 namespace blink {
 
 LayoutNGBlockFlow::LayoutNGBlockFlow(Element* element)
     : LayoutBlockFlow(element) {}
 
 bool LayoutNGBlockFlow::isOfType(LayoutObjectType type) const {
   return type == LayoutObjectNGBlockFlow || LayoutBlockFlow::isOfType(type);
 }
 
 void LayoutNGBlockFlow::layoutBlock(bool relayoutChildren) {
   LayoutAnalyzer::BlockScope analyzer(*this);
 
   auto* constraint_space = NGConstraintSpace::CreateFromLayoutObject(*this);
 
   // TODO(layout-dev): This should be created in the constructor once instead.
   // There is some internal state which needs to be cleared between layout
   // passes (probably FirstChild(), etc).
   m_box = new NGBlockNode(this);
 
-  RefPtr<NGLayoutResult> result = m_box->Layout(constraint_space);
+  RefPtr<NGLayoutResult> result =
+      m_box->Layout(constraint_space, /* break_token */ nullptr);

[Gleb Lanbin, 2017/02/24 21:51:27]

make break_token optional?

[ikilpatrick, 2017/02/25 00:57:21]

Done.

 
   if (isOutOfFlowPositioned()) {
     // In legacy layout, abspos differs from regular blocks in that abspos
     // blocks position themselves in their own layout, instead of getting
     // positioned by their parent. So it we are a positioned block in a legacy-
     // layout containing block, we have to emulate this positioning.
     // Additionally, until we natively support abspos in LayoutNG, this code
     // will also be reached though the layoutPositionedObjects call in
     // NGBlockNode::CopyFragmentDataToLayoutBox.
     LogicalExtentComputedValues computedValues;
     computeLogicalWidth(computedValues);
     setLogicalLeft(computedValues.m_position);
     computeLogicalHeight(logicalHeight(), logicalTop(), computedValues);
     setLogicalTop(computedValues.m_position);
   }
 
   for (auto& descendant : result->OutOfFlowDescendants())
     descendant->UseOldOutOfFlowPositioning();
   clearNeedsLayout();
 }
 
 }  // namespace blink