[LayoutNG] Refactor the fieldset Layout() function

Refactor the fieldset Layout() function to increase readability. This
CL should have no functional change.

Bug: 875235
Change-Id: Ie9081f419fd06f99a50c3def3747b48d08471c9d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102765
Commit-Queue: Alison Maher <almaher@microsoft.com>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750623}

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

@@ -12,6 +12,7 @@
 
 namespace blink {
 
+enum class NGBreakStatus;
 class NGBlockBreakToken;
 class NGConstraintSpace;
 
@@ -28,6 +29,15 @@ class CORE_EXPORT NGFieldsetLayoutAlgorithm
       const MinMaxSizesInput&) const override;
 
  private:
+  NGBreakStatus LayoutChildren();
+  NGBreakStatus LayoutLegend(
+      NGBlockNode& legend,
+      scoped_refptr<const NGBlockBreakToken> legend_break_token);
+  NGBreakStatus LayoutFieldsetContent(
+      NGBlockNode& fieldset_content,
+      scoped_refptr<const NGBlockBreakToken> content_break_token,
+      const LogicalSize adjusted_padding_box_size);
+
   const NGConstraintSpace CreateConstraintSpaceForLegend(
       NGBlockNode legend,
       LogicalSize available_size,
@@ -38,7 +48,30 @@ class CORE_EXPORT NGFieldsetLayoutAlgorithm
       LogicalSize padding_box_size,
       LayoutUnit block_offset);
 
+  const WritingMode writing_mode_;
+
   const NGBoxStrut border_padding_;
+  NGBoxStrut borders_;
+  NGBoxStrut padding_;
+
+  // The border and padding after adjusting to ensure that the leading border
+  // and padding are only applied to the first fragment.
+  NGBoxStrut adjusted_border_padding_;
+
+  // The result of borders_ after positioning the fieldset's legend element.
+  NGBoxStrut borders_with_legend_;
+
+  LayoutUnit block_start_padding_edge_;
+  LayoutUnit intrinsic_block_size_;
+  LogicalSize border_box_size_;
+
+  // If true, this indicates the block_start_padding_edge_ had changed from its
+  // initial value during the current layout pass.
+  bool block_start_padding_edge_adjusted_ = false;
+
+  // If true, this indicates that either the entire legend or part of the
+  // legend needs to be laid out during the current layout pass.
+  bool legend_needs_layout_ = false;
 };
 
 }  // namespace blink

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

@@ -38,7 +38,8 @@ class NGFieldsetLayoutAlgorithmTest
   MinMaxSizes RunComputeMinMaxSizes(NGBlockNode node) {
     NGConstraintSpace space = ConstructBlockLayoutTestConstraintSpace(
         WritingMode::kHorizontalTb, TextDirection::kLtr,
-        LogicalSize(LayoutUnit(), LayoutUnit()));
+        LogicalSize(LayoutUnit(), LayoutUnit()), false,
+        node.CreatesNewFormattingContext());
     NGFragmentGeometry fragment_geometry =
         CalculateInitialMinMaxFragmentGeometry(space, node);