[LayoutNG] Split up NGColumnLayoutAlgorithm::Layout().

This is in preparation for column-span:all support, where we'll need to
support multiple column rows within one and the same multicol container
fragment.

Change-Id: Ia1189ea1526faa37d1a0c51b2dadfc7a9d40b0bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1765509
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689623}

third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm.h

@@ -28,6 +28,8 @@ class CORE_EXPORT NGColumnLayoutAlgorithm
       const MinMaxSizeInput&) const override;
 
  private:
+  void LayoutRow(scoped_refptr<const NGBlockBreakToken> next_column_token);
+
   LogicalSize CalculateColumnSize(const LogicalSize& content_box_size);
   LayoutUnit CalculateBalancedColumnBlockSize(const LogicalSize& column_size,
                                               int column_count);
@@ -52,6 +54,11 @@ class CORE_EXPORT NGColumnLayoutAlgorithm
 
   const NGBoxStrut border_padding_;
   const NGBoxStrut border_scrollbar_padding_;
+  LogicalSize content_box_size_;
+  int used_column_count_;
+  LayoutUnit column_inline_size_;
+  LayoutUnit column_inline_progression_;
+  LayoutUnit intrinsic_block_size_;
 };
 
 }  // namespace blink