Move ProcessedSource#sorted_tokens to be a public method.

lib/rubocop/ast/processed_source.rb

@@ -177,6 +177,14 @@ def last_token_of(range_or_node)
         sorted_tokens[last_token_index(range_or_node)]
       end
 
+      # The tokens list is always sorted by token position, except for cases when heredoc
+      # is passed as a method argument. In this case tokens are interleaved by
+      # heredoc contents' tokens.
+      def sorted_tokens
+        # Use stable sort.
+        @sorted_tokens ||= tokens.sort_by.with_index { |token, i| [token.begin_pos, i] }
+      end
+
       private
 
       def comment_index
@@ -272,14 +280,6 @@ def last_token_index(range_or_node)
         sorted_tokens.bsearch_index { |token| token.end_pos >= end_pos }
       end
 
-      # The tokens list is always sorted by token position, except for cases when heredoc
-      # is passed as a method argument. In this case tokens are interleaved by
-      # heredoc contents' tokens.
-      def sorted_tokens
-        # Use stable sort.
-        @sorted_tokens ||= tokens.sort_by.with_index { |token, i| [token.begin_pos, i] }
-      end
-
       def source_range(range_or_node)
         if range_or_node.respond_to?(:source_range)
           range_or_node.source_range