[LayoutNG] Store the containing block offset

This change adds the containing block offset inside
NGPhysicalOutOfFlowPositionedNode and NGLogicalOutOfFlowPositionedNode.
This is part of the work for handling layout of positioned elements at
the fragmentainer level rather than at the containing block level.

A follow-up change will make use of this offset to compute where the
layout of an OOF positioned node should start in a multicolumn context.

Bug: 1079031
Change-Id: I2e3370a4ec0a4011203d0c3e916a64584aceaa2e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321405
Commit-Queue: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Reviewed-by: Alison Maher <almaher@microsoft.com>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793618}

third_party/blink/renderer/core/layout/ng/ng_container_fragment_builder.cc

@@ -73,12 +73,17 @@ void NGContainerFragmentBuilder::PropagateChildData(
         if (!containing_block_fragment)
           containing_block_fragment = fragment;
 
+        LogicalOffset containing_block_offset =
+            descendant.containing_block_offset.ConvertToLogical(
+                GetWritingMode(), Direction(), child.Size(), PhysicalSize());
+        containing_block_offset += child_offset;
+
         NGLogicalStaticPosition static_position =
             descendant.static_position.ConvertToLogical(
                 GetWritingMode(), Direction(), PhysicalSize());
         oof_positioned_fragmentainer_descendants_.emplace_back(
             descendant.node, static_position, descendant.inline_container,
-            /* needs_block_offset_adjustment */ false,
+            /* needs_block_offset_adjustment */ false, containing_block_offset,
             containing_block_fragment);
       }
     }

third_party/blink/renderer/core/layout/ng/ng_out_of_flow_positioned_node.h

@@ -37,17 +37,20 @@ struct CORE_EXPORT NGPhysicalOutOfFlowPositionedNode {
   NGPhysicalStaticPosition static_position;
   // Continuation root of the optional inline container.
   const LayoutInline* inline_container;
+  PhysicalOffset containing_block_offset;
   scoped_refptr<const NGPhysicalContainerFragment> containing_block_fragment;
 
   NGPhysicalOutOfFlowPositionedNode(
       NGBlockNode node,
       NGPhysicalStaticPosition static_position,
       const LayoutInline* inline_container = nullptr,
+      PhysicalOffset containing_block_offset = PhysicalOffset(),
       scoped_refptr<const NGPhysicalContainerFragment>
           containing_block_fragment = nullptr)
       : node(node),
         static_position(static_position),
         inline_container(inline_container),
+        containing_block_offset(containing_block_offset),
         containing_block_fragment(std::move(containing_block_fragment)) {
     DCHECK(!inline_container ||
            inline_container == inline_container->ContinuationRoot());
@@ -66,6 +69,7 @@ struct NGLogicalOutOfFlowPositionedNode {
   // Continuation root of the optional inline container.
   const LayoutInline* inline_container;
   bool needs_block_offset_adjustment;
+  LogicalOffset containing_block_offset;
   scoped_refptr<const NGPhysicalContainerFragment> containing_block_fragment;
 
   NGLogicalOutOfFlowPositionedNode(
@@ -73,12 +77,14 @@ struct NGLogicalOutOfFlowPositionedNode {
       NGLogicalStaticPosition static_position,
       const LayoutInline* inline_container = nullptr,
       bool needs_block_offset_adjustment = false,
+      LogicalOffset containing_block_offset = LogicalOffset(),
       scoped_refptr<const NGPhysicalContainerFragment>
           containing_block_fragment = nullptr)
       : node(node),
         static_position(static_position),
         inline_container(inline_container),
         needs_block_offset_adjustment(needs_block_offset_adjustment),
+        containing_block_offset(containing_block_offset),
         containing_block_fragment(std::move(containing_block_fragment)) {
     DCHECK(!inline_container ||
            inline_container == inline_container->ContinuationRoot());

third_party/blink/renderer/core/layout/ng/ng_physical_box_fragment.cc

@@ -163,7 +163,13 @@ NGPhysicalBoxFragment::RareData::RareData(NGBoxFragmentBuilder* builder,
         descendant.node,
         descendant.static_position.ConvertToPhysical(
             builder->Style().GetWritingMode(), builder->Direction(), size),
-        descendant.inline_container, descendant.containing_block_fragment);
+        descendant.inline_container,
+        descendant.containing_block_offset.ConvertToPhysical(
+            builder->Style().GetWritingDirection(), size,
+            descendant.containing_block_fragment
+                ? descendant.containing_block_fragment->Size()
+                : PhysicalSize()),
+        descendant.containing_block_fragment);
   }
 }