Issue #146 - Part 2: Remove custom table painting component.

Since we're now putting table borders and backgrounds properly in the
display lists, we no longer need this custom component to do this work
for us.

layout/tables/nsTableRowGroupFrame.cpp

@@ -154,46 +154,6 @@ nsTableRowGroupFrame::InitRepeatedFrame(nsTableRowGroupFrame* aHeaderFooterFrame
   return NS_OK;
 }
 
-/**
- * We need a custom display item for table row backgrounds. This is only used
- * when the table row is the root of a stacking context (e.g., has 'opacity').
- * Table row backgrounds can extend beyond the row frame bounds, when
- * the row contains row-spanning cells.
- */
-class nsDisplayTableRowGroupBackground : public nsDisplayTableItem {
-public:
-  nsDisplayTableRowGroupBackground(nsDisplayListBuilder* aBuilder,
-                                   nsTableRowGroupFrame* aFrame) :
-    nsDisplayTableItem(aBuilder, aFrame) {
-    MOZ_COUNT_CTOR(nsDisplayTableRowGroupBackground);
-  }
-#ifdef NS_BUILD_REFCNT_LOGGING
-  virtual ~nsDisplayTableRowGroupBackground() {
-    MOZ_COUNT_DTOR(nsDisplayTableRowGroupBackground);
-  }
-#endif
-
-  virtual void Paint(nsDisplayListBuilder* aBuilder,
-                     nsRenderingContext* aCtx) override;
-
-  NS_DISPLAY_DECL_NAME("TableRowGroupBackground", TYPE_TABLE_ROW_GROUP_BACKGROUND)
-};
-
-void
-nsDisplayTableRowGroupBackground::Paint(nsDisplayListBuilder* aBuilder,
-                                        nsRenderingContext* aCtx)
-{
-  auto rgFrame = static_cast<nsTableRowGroupFrame*>(mFrame);
-  TableBackgroundPainter painter(rgFrame->GetTableFrame(),
-                                 TableBackgroundPainter::eOrigin_TableRowGroup,
-                                 mFrame->PresContext(), *aCtx,
-                                 mVisibleRect, ToReferenceFrame(),
-                                 aBuilder->GetBackgroundPaintFlags());
-
-  DrawResult result = painter.PaintRowGroup(rgFrame);
-  nsDisplayTableItemGeometry::UpdateDrawResult(this, result);
-}
-
 // Handle the child-traversal part of DisplayGenericTablePart
 static void
 DisplayRows(nsDisplayListBuilder* aBuilder, nsFrame* aFrame,