Use Layout Opportunity Iterator to position new FC blocks.

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h

Index: third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
index 2e6f19cbc42c11b6196256e983f929d068558de6..8be33a1922f87eefa8b861090ded614e1843843c 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
@@ -9,6 +9,7 @@
 #include "core/layout/ng/geometry/ng_margin_strut.h"
 #include "core/layout/ng/ng_block_break_token.h"
 #include "core/layout/ng/ng_block_node.h"
+#include "core/layout/ng/ng_box_fragment.h"
 #include "core/layout/ng/ng_constraint_space_builder.h"
 #include "core/layout/ng/ng_layout_algorithm.h"
 #include "platform/wtf/RefPtr.h"
@@ -45,11 +46,16 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
                               const NGConstraintSpace& space);
 
   // Creates a new constraint space for the current child.
-  RefPtr<NGConstraintSpace> CreateConstraintSpaceForChild(NGLayoutInputNode*);
-  void PrepareChildLayout(NGLayoutInputNode*);
-  void FinishChildLayout(NGLayoutInputNode*,
-                         NGConstraintSpace*,
-                         RefPtr<NGLayoutResult>);
+  RefPtr<NGConstraintSpace> CreateConstraintSpaceForChild(
+      const NGLogicalOffset& child_bfc_offset,
+      NGLayoutInputNode*);
+  NGLogicalOffset PrepareChildLayout(NGLayoutInputNode*);
+
+  void FinishChildLayout(const NGConstraintSpace*, NGLayoutResult*);
+
+  void FinishFloatChildLayout(const ComputedStyle&,
+                              const NGConstraintSpace&,
+                              const NGLayoutResult*);
 
   // Final adjustments before fragment creation. We need to prevent the
   // fragment from crossing fragmentainer boundaries, and rather create a break
@@ -63,6 +69,22 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
   NGLogicalOffset CalculateLogicalOffset(
       const WTF::Optional<NGLogicalOffset>& known_fragment_offset);
 
+  // Positions the fragment that establishes a new formatting context.
+  NGLogicalOffset PositionNewFc(const NGBoxFragment&,
+                                const NGConstraintSpace* child_space);
+
+  // Positions the fragment that knows its BFC offset.
+  NGLogicalOffset PositionWithBfcOffset(const NGBoxFragment&);
+
+  // Positions using the parent BFC offset.
+  // Fragment doesn't know its offset but we can still calculate its BFC
+  // position because the parent fragment's BFC is known.
+  // Example:
+  //   BFC Offset is known here because of the padding.
+  //   <div style="padding: 1px">
+  //     <div id="empty-div" style="margins: 1px"></div>
+  NGLogicalOffset PositionWithParentBfc();
+
   NGConstraintSpaceBuilder space_builder_;
 
   NGBoxStrut border_and_padding_;