Update our treatment of repeating headers in tables

third_party/WebKit/Source/core/paint/TableSectionPainter.cpp

Index: third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp b/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
index f1f68fd79263c9a999934a5b0a683a615307427e..d54f695f5f03300d2fb12009fab555036e3b4f02 100644
--- a/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
@@ -33,8 +33,10 @@ void TableSectionPainter::PaintRepeatingHeaderGroup(
   LayoutUnit header_group_offset = table->BlockOffsetToFirstRepeatableHeader();
   // The header may have a pagination strut before it so we need to account for
   // that when establishing its position.
+  LayoutUnit strut_on_first_row;
   if (LayoutTableRow* row = layout_table_section_.FirstRow())
-    header_group_offset += row->PaginationStrut();
+    strut_on_first_row = row->PaginationStrut();
+  header_group_offset += strut_on_first_row;
   LayoutUnit offset_to_next_page =
       page_height - IntMod(header_group_offset, page_height);
   // Move paginationOffset to the top of the next page.
@@ -59,11 +61,16 @@ void TableSectionPainter::PaintRepeatingHeaderGroup(
                paint_offset.Y() + total_height_of_rows);
 
   while (pagination_offset.Y() < bottom_bound) {
+    LayoutPoint nested_offset =
+        pagination_offset +
+        LayoutPoint(LayoutUnit(), table->RowOffsetFromRepeatingHeader() -

[mstensho (USE GERRIT), 2017/05/22 10:40:44]

If we really want to re-introduce nesting:

Thanks to the current coding style, I think this would look prettier if you
instead did this as part of a separate LayoutPoint::Move(LayoutUnit, LayoutUnit)
step. Maybe even a separate LayoutUnit declaration step for the y thing.

[rhogan, 2017/05/22 18:06:04]

Done.

+                                      layout_table_section_.LogicalHeight() +
+                                      strut_on_first_row);
     if (item_to_paint == kPaintCollapsedBorders) {
-      PaintCollapsedSectionBorders(paint_info, pagination_offset,
+      PaintCollapsedSectionBorders(paint_info, nested_offset,
                                    current_border_value);
     } else {
-      PaintSection(paint_info, pagination_offset);
+      PaintSection(paint_info, nested_offset);
     }
     pagination_offset.Move(0, page_height.ToInt());
   }