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

third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.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 NGFragmentBuilder_h
 #define NGFragmentBuilder_h
 
 #include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_floating_object.h"
@@ skipping 17 matching lines @@
   NGFragmentBuilder& SetInlineSize(LayoutUnit);
   NGFragmentBuilder& SetBlockSize(LayoutUnit);
   NGLogicalSize Size() const { return size_; }
 
   NGFragmentBuilder& SetInlineOverflow(LayoutUnit);
   NGFragmentBuilder& SetBlockOverflow(LayoutUnit);
 
   NGFragmentBuilder& AddChild(RefPtr<NGLayoutResult>, const NGLogicalOffset&);
   NGFragmentBuilder& AddChild(RefPtr<NGPhysicalFragment>,
                               const NGLogicalOffset&);
+
   NGFragmentBuilder& AddFloatingObject(NGFloatingObject*,
                                        const NGLogicalOffset&);
 
   NGFragmentBuilder& SetBfcOffset(const NGLogicalOffset& offset);
 
   NGFragmentBuilder& AddUnpositionedFloat(NGFloatingObject* floating_object);
 
   // Builder has non-trivial out-of-flow descendant methods.
   // These methods are building blocks for implementation of
   // out-of-flow descendants by layout algorithms.
@@ skipping 20 matching lines @@
   //
   // See layout part for builder interaction.
   NGFragmentBuilder& AddOutOfFlowChildCandidate(NGBlockNode*, NGLogicalOffset);
 
   void GetAndClearOutOfFlowDescendantCandidates(WeakBoxList*,
                                                 Vector<NGStaticPosition>*);
 
   NGFragmentBuilder& AddOutOfFlowDescendant(NGBlockNode*,
                                             const NGStaticPosition&);
 
-  void SetBreakToken(NGBreakToken* token) {
-    DCHECK(!break_token_);
-    break_token_ = token;
+  NGFragmentBuilder& SetUsedBlockSize(LayoutUnit used_block_size) {

[mstensho (USE GERRIT), 2017/02/27 13:44:36]

I think this one needs documentation, and perhaps a better name, since it does
two things: set used block size and mark that we did break.

[ikilpatrick, 2017/02/27 18:50:09]

PTAL.

+    used_block_size_ = used_block_size;
+    did_break_ = true;
+    return *this;
   }
-  bool HasBreakToken() const { return break_token_; }
 
   NGFragmentBuilder& SetEndMarginStrut(const NGMarginStrut& from) {
     end_margin_strut_ = from;
     return *this;
   }
 
   // Offsets are not supposed to be set during fragment construction, so we
   // do not provide a setter here.
 
   // Creates the fragment. Can only be called once.
   RefPtr<NGLayoutResult> ToBoxFragment();
   RefPtr<NGPhysicalTextFragment> ToTextFragment(unsigned index,
                                                 unsigned start_offset,
                                                 unsigned end_offset);
 
   // Mutable list of floats that need to be positioned.
   Vector<Persistent<NGFloatingObject>>& MutableUnpositionedFloats() {
     return unpositioned_floats_;
   }
 
   // List of floats that need to be positioned.
   const Vector<Persistent<NGFloatingObject>>& UnpositionedFloats() const {
     return unpositioned_floats_;
   }
 
   const WTF::Optional<NGLogicalOffset>& BfcOffset() const {
     return bfc_offset_;
   }
 
+  bool DidBreak() const { return did_break_; }
+
  private:
   // Out-of-flow descendant placement information.
   // The generated fragment must compute NGStaticPosition for all
   // out-of-flow descendants.
   // The resulting NGStaticPosition gets derived from:
   // 1. The offset of fragment's child.
   // 2. The static position of descendant wrt child.
   //
   // A child can be:
   // 1. A descendant itself. In this case, descendant position is (0,0).
@@ skipping 11 matching lines @@
   TextDirection direction_;
 
   Persistent<NGLayoutInputNode> node_;
 
   NGLogicalSize size_;
   NGLogicalSize overflow_;
 
   Vector<RefPtr<NGPhysicalFragment>> children_;
   Vector<NGLogicalOffset> offsets_;
 
+  bool did_break_;
+  LayoutUnit used_block_size_;
+
+  Persistent<HeapVector<Member<NGBreakToken>>> child_break_tokens_;
+
   WeakBoxList out_of_flow_descendant_candidates_;
   Vector<OutOfFlowPlacement> out_of_flow_candidate_placements_;
 
   WeakBoxList out_of_flow_descendants_;
   Vector<NGStaticPosition> out_of_flow_positions_;
 
   // Floats that need to be positioned by the next in-flow fragment that can
   // determine its block position in space.
   Vector<Persistent<NGFloatingObject>> unpositioned_floats_;
 
   Vector<NGLogicalOffset> floating_object_offsets_;
   Vector<Persistent<NGFloatingObject>> positioned_floats_;
 
-  Persistent<NGBreakToken> break_token_;
-
   WTF::Optional<NGLogicalOffset> bfc_offset_;
   NGMarginStrut end_margin_strut_;
 };
 
 }  // namespace blink
 
 #endif  // NGFragmentBuilder