[LayoutNG] Acutally use CurrentFragment within LayoutNGMixin::Paint.

There should be no behaviour change.

Change-Id: Ic9b22f18358779f9808c7e2aa2f37422e9696936
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1976939Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Aleks Totic <atotic@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726570}

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

@@ -40,10 +40,8 @@ void LayoutNGMixin<Base>::Paint(const PaintInfo& paint_info) const {
     return;
   }
 
-  if (const NGLayoutResult* result = Base::GetCachedLayoutResult()) {
-    NGBoxFragmentPainter(To<NGPhysicalBoxFragment>(result->PhysicalFragment()))
-        .Paint(paint_info);
-  }
+  if (const NGPhysicalBoxFragment* fragment = CurrentFragment())
+    NGBoxFragmentPainter(*fragment).Paint(paint_info);
 }
 
 // The current fragment from the last layout cycle for this box.