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

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.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 NGBlockLayoutAlgorithm_h
 #define NGBlockLayoutAlgorithm_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_column_mapper.h"
 #include "core/layout/ng/ng_fragment_builder.h"
 #include "core/layout/ng/ng_layout_algorithm.h"
 #include "core/layout/ng/ng_units.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class ComputedStyle;
 class NGBlockBreakToken;
 class NGConstraintSpace;
 class NGConstraintSpaceBuilder;
 class NGInlineNode;
 class NGLayoutResult;
-class NGPhysicalFragment;
 
 // A class for general block layout (e.g. a <div> with no special style).
 // Lays out the children in sequence.
 class CORE_EXPORT NGBlockLayoutAlgorithm : public NGLayoutAlgorithm {
  public:
   // Default constructor.
   // @param node The input node to perform layout upon.
   // @param space The constraint space which the algorithm should generate a
   //              fragment within.
   // @param break_token The break token from which the layout should start.
   NGBlockLayoutAlgorithm(NGBlockNode* node,
                          NGConstraintSpace* space,
-                         NGBreakToken* break_token = nullptr);
+                         NGBlockBreakToken* break_token = nullptr);
 
   Optional<MinAndMaxContentSizes> ComputeMinAndMaxContentSizes() const override;
   RefPtr<NGLayoutResult> Layout() override;
 
  private:
   NGBoxStrut CalculateMargins(const NGConstraintSpace& space,
                               const ComputedStyle& style);
 
   // Creates a new constraint space for the current child.
   NGConstraintSpace* CreateConstraintSpaceForCurrentChild();
   void FinishCurrentChildLayout(RefPtr<NGLayoutResult>);
 
   // Layout inline children.
   void LayoutInlineChildren(NGInlineNode*);
 
-  // Proceed to the next sibling that still needs layout.
-  //
-  // @param child_fragment The newly created fragment for the current child.
-  // @return true if we can continue to lay out, or false if we need to abort
-  // due to a fragmentainer break.
-  bool ProceedToNextUnfinishedSibling(NGPhysicalFragment* child_fragment);
-
-  // Set a break token which contains enough information to be able to resume
-  // layout in the next fragmentainer.
-  void SetPendingBreakToken(NGBlockBreakToken*);
-
-  // Check if we have a pending break token set. Once we have set a pending
-  // break token, we cannot set another one. First we need to abort layout in
-  // the current fragmentainer and resume in the next one.
-  bool HasPendingBreakToken() const;
-
   // Final adjusstments before fragment creation. We need to prevent the

[cbiesinger, 2017/02/27 19:09:37]

While you're touching the related code, do you want to fix this typo?
(adjusstments -> adjustments)

[ikilpatrick, 2017/02/27 19:29:34]

Done.

   // fragment from crossing fragmentainer boundaries, and rather create a break
   // token if we're out of space.
   void FinalizeForFragmentation();
 
-  // Return the break token, if any, at which we resumed layout after a
-  // previous break.
-  NGBlockBreakToken* CurrentBlockBreakToken() const;
-
-  // Return the block offset of the previous break, in the fragmented flow
-  // coordinate space, relatively to the start edge of this block.
-  LayoutUnit PreviousBreakOffset() const;
-
-  // Return the offset of the potential next break, in the fragmented flow
-  // coordinate space, relatively to the start edge of this block.
-  LayoutUnit NextBreakOffset() const;
-
-  // Get the amount of block space left in the current fragmentainer for the
-  // child that is about to be laid out.
-  LayoutUnit SpaceAvailableForCurrentChild() const;
-
-  LayoutUnit BorderEdgeForCurrentChild() const {
-    // TODO(mstensho): Need to take care of margin collapsing somehow. We
-    // should at least attempt to estimate what the top margin is going to be.
-    return content_size_;
-  }
-
   // Calculates logical offset for the current fragment using either
   // {@code content_size_} when the fragment doesn't know it's offset
   // or {@code known_fragment_offset} if the fragment knows it's offset
   // @return Fragment's offset relative to the fragment's parent.
   NGLogicalOffset CalculateLogicalOffset(
       const WTF::Optional<NGLogicalOffset>& known_fragment_offset);
 
   // Updates the fragment's BFC offset if it's not already set.
   void UpdateFragmentBfcOffset(const NGLogicalOffset& offset);
 
@@ skipping 14 matching lines @@
   const NGConstraintSpace& CurrentChildConstraintSpace() const {
     return *space_for_current_child_.get();
   }
 
   const ComputedStyle& Style() const { return node_->Style(); }
 
   Persistent<NGBlockNode> node_;
   Persistent<NGConstraintSpace> constraint_space_;
 
   // The break token from which we are currently resuming layout.
-  Persistent<NGBreakToken> break_token_;
+  Persistent<NGBlockBreakToken> break_token_;
 
   std::unique_ptr<NGFragmentBuilder> builder_;
   Persistent<NGConstraintSpaceBuilder> space_builder_;
   Persistent<NGConstraintSpace> space_for_current_child_;
   Persistent<NGLayoutInputNode> current_child_;
 
-  // Mapper from the fragmented flow coordinate space coordinates to visual
-  // coordinates. Only set on fragmentation context roots, such as multicol
-  // containers. Keeps track of the current fragmentainer.
-  Persistent<NGColumnMapper> fragmentainer_mapper_;
-
   NGBoxStrut border_and_padding_;
   LayoutUnit content_size_;
   LayoutUnit max_inline_size_;
   // MarginStrut for the previous child.
   NGMarginStrut curr_margin_strut_;
   NGLogicalOffset bfc_offset_;
   NGLogicalOffset curr_bfc_offset_;
   NGBoxStrut curr_child_margins_;
 };
 
 }  // namespace blink
 
 #endif  // NGBlockLayoutAlgorithm_h