[LayoutNG] Make fieldset legends monolithic

Previously, we had made the legends fragment in the following change
https://chromium-review.googlesource.com/c/chromium/src/+/2090762. In
this other change
https://chromium-review.googlesource.com/c/chromium/src/+/2263353
we decided to not break borders for now. Because the legend is part of
the fieldset border, we now want to treat the legend as monolithic.

We still have logic for breaking the fieldset border, this will be
addressed in a follow up change.

Bug: 1097012
Change-Id: Iace252447063eb694c47fb9eea2a406ba2fe79d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353354
Commit-Queue: Ana Sollano Kim <ansollan@microsoft.com>
Reviewed-by: Alison Maher <almaher@microsoft.com>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798528}

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

@@ -37,9 +37,7 @@ class CORE_EXPORT NGFieldsetLayoutAlgorithm
 
  private:
   NGBreakStatus LayoutChildren();
-  NGBreakStatus LayoutLegend(
-      NGBlockNode& legend,
-      scoped_refptr<const NGBlockBreakToken> legend_break_token);
+  void LayoutLegend(NGBlockNode& legend);
   NGBreakStatus LayoutFieldsetContent(
       NGBlockNode& fieldset_content,
       scoped_refptr<const NGBlockBreakToken> content_break_token,
@@ -49,13 +47,11 @@ class CORE_EXPORT NGFieldsetLayoutAlgorithm
   const NGConstraintSpace CreateConstraintSpaceForLegend(
       NGBlockNode legend,
       LogicalSize available_size,
-      LogicalSize percentage_size,
-      LayoutUnit block_offset);
+      LogicalSize percentage_size);
   const NGConstraintSpace CreateConstraintSpaceForFieldsetContent(
       NGBlockNode fieldset_content,
       LogicalSize padding_box_size,
       LayoutUnit block_offset);
-
   bool IsFragmentainerOutOfSpace(LayoutUnit block_offset) const;
 
   const WritingMode writing_mode_;
@@ -76,10 +72,6 @@ class CORE_EXPORT NGFieldsetLayoutAlgorithm
   // fragments.
   LayoutUnit consumed_border_block_start_;
 
-  // If true, this indicates that the legend broke during the current layout
-  // pass.
-  bool legend_broke_ = false;
-
   // If true, the legend is taller than the block-start border, so that it
   // sticks below it, allowing for a class C breakpoint [1] before any fieldset
   // content.