[LayoutNG] Disable NGBoxFragmentPainter for multi-columns.

We only hit this section of code when LayoutNGBlockFragmentation is
enabled. Currently the NGBoxFragmentPainter doesn't support painting
column rules correctly.

This will have to be added before LayoutNGBlockFragmentation is enabled.

Bug: 988015
Change-Id: I40f2f873814f861e370428972fb52b12f3e4907b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869445Reviewed-by: Koji Ishii <kojii@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712243}

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

@@ -283,17 +283,25 @@ void LayoutNGBlockFlowMixin<Base>::Paint(const PaintInfo& paint_info) const {
     }
   }
 
+  // |NGBoxFragmentPainter| currently doesn't support column rules.
+  if (UNLIKELY(Base::MultiColumnFlowThread())) {
+    Base::Paint(paint_info);
+    return;
+  }
+
+  if (const NGPaintFragment* paint_fragment = PaintFragment()) {
+    NGBoxFragmentPainter(*paint_fragment).Paint(paint_info);
+    return;
+  }
+
   if (UNLIKELY(RuntimeEnabledFeatures::LayoutNGFragmentPaintEnabled())) {
     if (const NGPhysicalBoxFragment* fragment = CurrentFragment()) {
-      NGBoxFragmentPainter(*fragment, PaintFragment()).Paint(paint_info);
+      NGBoxFragmentPainter(*fragment).Paint(paint_info);
       return;
     }
   }
 
-  if (const NGPaintFragment* paint_fragment = PaintFragment())
-    NGBoxFragmentPainter(*paint_fragment).Paint(paint_info);
-  else
-    LayoutBlockFlow::Paint(paint_info);
+  Base::Paint(paint_info);
 }
 
 template <typename Base>