[TablesNG] Box order for painting

Use box order to resolve intersection edge precedence.

Makes 9 additional tests pass:

css2.1/20110323/border-conflict-element-001d.htm
external/wpt/css/CSS2/tables/border-conflict-element-001d.xht
external/wpt/css/CSS2/tables/border-conflict-element-001e.xht
fast/css/table-rules-attribute-groups-with-frame.html
fast/table/colgroup-spanning-groups-rules.html
fast/table/border-collapsing/002-vertical.html
fast/table/border-collapsing/002.html
tables/mozilla/core/table_rules.html
tables/mozilla/marvin/x_table_rules_groups.xml

Bug: 958381
Change-Id: I53f87d716aada00edec5f06129842fc1fc10eb68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519882
Commit-Queue: Aleks Totic <atotic@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824701}

third_party/blink/renderer/core/layout/ng/table/ng_table_borders.h

@@ -80,6 +80,11 @@ class NGTableBorders : public RefCounted<NGTableBorders> {
   struct Edge {
     scoped_refptr<const ComputedStyle> style;
     EdgeSide edge_side;
+    // Box order is used to compute edge painting precedence.
+    // Lower box order has precedence.
+    // The order value is defined as "box visited index" while
+    // computing collapsed edges.
+    wtf_size_t box_order;
   };
 
   static LayoutUnit BorderWidth(const ComputedStyle* style,
@@ -172,6 +177,10 @@ class NGTableBorders : public RefCounted<NGTableBorders> {
                        edges_[edge_index].edge_side);
   }
 
+  wtf_size_t BoxOrder(wtf_size_t edge_index) const {
+    return edges_[edge_index].box_order;
+  }
+
   using Edges = Vector<Edge>;
 
   struct Section {
@@ -219,8 +228,9 @@ class NGTableBorders : public RefCounted<NGTableBorders> {
                     wtf_size_t start_column,
                     wtf_size_t rowspan,
                     wtf_size_t colspan,
-                    const ComputedStyle* source_style,
+                    const ComputedStyle& source_style,
                     EdgeSource source,
+                    wtf_size_t box_order,
                     WritingDirectionMode table_writing_direction,
                     wtf_size_t section_index = kNotFound);
 
@@ -297,13 +307,15 @@ class NGTableBorders : public RefCounted<NGTableBorders> {
   void MergeRowAxisBorder(wtf_size_t start_row,
                           wtf_size_t start_column,
                           wtf_size_t colspan,
-                          const ComputedStyle* source_style,
+                          const ComputedStyle& source_style,
+                          wtf_size_t box_order,
                           EdgeSide side);
 
   void MergeColumnAxisBorder(wtf_size_t start_row,
                              wtf_size_t start_column,
                              wtf_size_t rowspan,
-                             const ComputedStyle* source_style,
+                             const ComputedStyle& source_style,
+                             wtf_size_t box_order,
                              EdgeSide side);
 
   void MarkInnerBordersAsDoNotFill(wtf_size_t start_row,

third_party/blink/renderer/core/paint/ng/ng_table_painters.cc

@@ -69,6 +69,16 @@ class NGTableCollapsedEdge {
 
   Color BorderColor() const { return borders_.BorderColor(edge_index_); }
 
+  int CompareBoxOrder(wtf_size_t other_edge_index) const {
+    wtf_size_t box_order = borders_.BoxOrder(edge_index_);
+    wtf_size_t other_box_order = borders_.BoxOrder(other_edge_index);
+    if (box_order < other_box_order)
+      return 1;
+    if (box_order > other_box_order)
+      return -1;
+    return 0;
+  }
+
   bool IsInlineAxis() const {
     DCHECK(Exists());
     DCHECK_NE(edge_index_, UINT_MAX);
@@ -103,7 +113,7 @@ class NGTableCollapsedEdge {
         // Paint border style comparison for paint has different
         // rules than for winning edge border (hidden does not win).
         if (lhs.border_style_ == rhs.border_style_)
-          return 0;
+          return lhs.CompareBoxOrder(rhs.edge_index_);
         if (rhs.border_style_ == EBorderStyle::kHidden)
           return 1;
         if (lhs.border_style_ == EBorderStyle::kHidden)