[LayoutNG] NGPhysicalFragment::CheckType() for columns.

Follow-up to CL:1669916

Change-Id: Ie98e1cbf0ed3cb90b41bdc682367474992bd1970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1676124
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672124}

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

@@ -367,7 +367,15 @@ void NGPhysicalFragment::CheckType() const {
         DCHECK(layout_object_.IsBox());
       }
       if (IsColumnBox()) {
-        // TODO(kojii): Column box can fail following checks, needs review.
+        // Column fragments are associated with the same layout object as their
+        // multicol container. The fragments themselves are regular in-flow
+        // block container fragments for most purposes.
+        DCHECK(layout_object_.IsLayoutBlockFlow());
+        DCHECK(IsBox());
+        DCHECK(!IsFloating());
+        DCHECK(!IsOutOfFlowPositioned());
+        DCHECK(!IsAtomicInline());
+        DCHECK(!IsBlockFormattingContextRoot());
         break;
       }
       if (layout_object_.IsLayoutNGListMarker()) {