message: Remove obsolete TODO and update interface comment.
diff: @@ -71,8 +71,11 @@ class ColumnSchemaScanner : public TreeContextPathVisitor {
  }
  protected:
  - // TODO(fangism): support specifying desired column characteristics, like
  - // flush_left.
  + // Mark the start of a new column for alignment.
  + // 'symbol' is a reference to the original source syntax subtree.
  + // 'properties' contains alignment configuration for the column.
  + // 'path' represents relative position within the enclosing syntax subtree,
  + // and is used as a key for ordering and matching columns.
  void ReserveNewColumn(const Symbol& symbol,
  const AlignmentColumnProperties& properties,
  const SyntaxTreePath& path);
  