Fragment that establishes new BFC knows it's BFC offset in parent space

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 NGBoxFragment;
 class NGConstraintSpace;
 class NGConstraintSpaceBuilder;
 class NGInlineNode;
 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.
@@ skipping 59 matching lines @@
   // 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 offset for the provided fragment which is relative to the
-  // fragment's parent.
-  NGLogicalOffset CalculateRelativeOffset(const NGBoxFragment& fragment);
+  // 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);
+
   NGLogicalOffset GetChildSpaceOffset() const {
     return NGLogicalOffset(border_and_padding_.inline_start, content_size_);
   }
 
   // Read-only Getters.
   const ComputedStyle& CurrentChildStyle() const {
     DCHECK(current_child_);
     return toNGBlockNode(current_child_)->Style();
   }
 
@@ skipping 31 matching lines @@
   // 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