[GridNG] Parsing of empty grid named lines for subgrid

In this CL we introduce the parsing of empty grid named lines used in a
subgrid's line name list.The web test grid-template-valid.html is now
a full pass and more cases with empty lines were added.

We'll address the serialization of empty lines in another CL, added a
TODO in |StyleBuilderConverter| to track it.

Bug: 618969
Change-Id: I55f55a1633d30ab94ca9b0046265e38c952f569f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3308413
Commit-Queue: Ana Sollano Kim <[email protected]>
Reviewed-by: Rune Lillesveen <[email protected]>
Reviewed-by: Ethan Jimenez <[email protected]>
Reviewed-by: Ian Kilpatrick <[email protected]>
Cr-Commit-Position: refs/heads/main@{#948155}

css/css-grid/subgrid/grid-template-valid.html

@@ -17,28 +17,38 @@
 test_valid_value("grid-template-rows", 'subgrid [a]');
 test_valid_value("grid-template-rows", 'subgrid [a] [b]');
 test_valid_value("grid-template-rows", 'subgrid [a] [b] [c]');
+test_valid_value("grid-template-rows", 'subgrid []');
 test_valid_value("grid-template-rows", 'subgrid [a] [b] [] [c]');
+test_valid_value("grid-template-rows", 'subgrid [] [] [] [c]');
+test_valid_value("grid-template-rows", 'subgrid [] [] [] []');
 test_valid_value("grid-template-rows", 'subgrid repeat(auto-fill, [a])');
 test_valid_value("grid-template-rows", 'subgrid [a] repeat(auto-fill, [b])');
 test_valid_value("grid-template-rows", 'subgrid [a] repeat(auto-fill, [b]) [c]');
+test_valid_value("grid-template-rows", 'subgrid [] repeat(auto-fill, []) []');
 test_valid_value("grid-template-rows", 'subgrid repeat(2, [a])');
 test_valid_value("grid-template-rows", 'subgrid repeat(2, [a] [b])');
 test_valid_value("grid-template-rows", 'subgrid [a] repeat(2, [b])');
 test_valid_value("grid-template-rows", 'subgrid [a] repeat(2, [b]) [c]');
+test_valid_value("grid-template-rows", 'subgrid [] repeat(2, []) []');
 test_valid_value("grid-template-rows", 'subgrid [a] repeat(2, [b]) repeat(auto-fill, [c]) [d]');
 
 test_valid_value("grid-template-columns", 'subgrid');
 test_valid_value("grid-template-columns", 'subgrid [a]');
 test_valid_value("grid-template-columns", 'subgrid [a] [b]');
 test_valid_value("grid-template-columns", 'subgrid [a] [b] [c]');
+test_valid_value("grid-template-columns", 'subgrid []');
 test_valid_value("grid-template-columns", 'subgrid [a] [b] [] [c]');
+test_valid_value("grid-template-columns", 'subgrid [] [] [] [c]');
+test_valid_value("grid-template-columns", 'subgrid [] [] [] []');
 test_valid_value("grid-template-columns", 'subgrid repeat(auto-fill, [a])');
 test_valid_value("grid-template-columns", 'subgrid [a] repeat(auto-fill, [b])');
 test_valid_value("grid-template-columns", 'subgrid [a] repeat(auto-fill, [b]) [c]');
+test_valid_value("grid-template-columns", 'subgrid [] repeat(auto-fill, []) []');
 test_valid_value("grid-template-columns", 'subgrid repeat(2, [a])');
 test_valid_value("grid-template-columns", 'subgrid repeat(2, [a] [b])');
 test_valid_value("grid-template-columns", 'subgrid [a] repeat(2, [b])');
 test_valid_value("grid-template-columns", 'subgrid [a] repeat(2, [b]) [c]');
+test_valid_value("grid-template-columns", 'subgrid [] repeat(2, []) []');
 test_valid_value("grid-template-columns", 'subgrid [a] repeat(2, [b]) repeat(auto-fill, [c]) [d]');
 
 </script>