Support multiple track sizes for grid-auto-{columns|rows}.

Support `<track-size>+` on the implicit track sizing properties,
grid-auto-columns and grid-auto-rows.

Differential Revision: https://phabricator.services.mozilla.com/D38408

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1339672
gecko-commit: 4e4bb211b6733d7a9d710118fe58834f631152a4
gecko-integration-branch: autoland
gecko-reviewers: emilio, mats

css/css-grid/parsing/grid-auto-columns-invalid.html

@@ -32,6 +32,7 @@
 // <track-size>+
 test_invalid_value("grid-auto-columns", "2em / 3em");
 test_invalid_value("grid-auto-columns", "auto, 10%");
+test_invalid_value("grid-auto-rows", "1px [a] 1px");
 </script>
 </body>
 </html>

css/css-grid/parsing/grid-auto-columns-valid.html

@@ -22,6 +22,7 @@
 test_valid_value("grid-auto-columns", "min-content");
 test_valid_value("grid-auto-columns", "max-content");
 test_valid_value("grid-auto-columns", "auto");
+test_valid_value("grid-auto-columns", "auto /**/", "auto");
 
 // minmax( <inflexible-breadth> , <track-breadth> )
 // <inflexible-breadth> = <length-percentage> | min-content | max-content | auto
@@ -47,6 +48,8 @@
 test_valid_value("grid-auto-columns", "fit-content(0px)");
 
 // <track-size>+
+test_valid_value("grid-auto-columns", "auto auto");
+test_valid_value("grid-auto-columns", "auto 10px");
 test_valid_value("grid-auto-columns", "1px 2px 3px 0px");
 test_valid_value("grid-auto-columns", "fit-content(1px) minmax(2px, 3px) 4px");
 </script>

css/css-grid/parsing/grid-auto-rows-invalid.html

@@ -31,6 +31,7 @@
 // <track-size>+
 test_invalid_value("grid-auto-rows", "2em / 3em");
 test_invalid_value("grid-auto-rows", "auto, 10%");
+test_invalid_value("grid-auto-rows", "1px [a] 1px");
 </script>
 </body>
 </html>

css/css-grid/parsing/grid-auto-rows-valid.html

@@ -22,6 +22,7 @@
 test_valid_value("grid-auto-rows", "min-content");
 test_valid_value("grid-auto-rows", "max-content");
 test_valid_value("grid-auto-rows", "auto");
+test_valid_value("grid-auto-rows", "auto /**/", "auto");
 
 // minmax( <inflexible-breadth> , <track-breadth> )
 // <inflexible-breadth> = <length-percentage> | min-content | max-content | auto
@@ -47,6 +48,8 @@
 test_valid_value("grid-auto-rows", "fit-content(0px)");
 
 // <track-size>+
+test_valid_value("grid-auto-rows", "auto auto");
+test_valid_value("grid-auto-rows", "auto 10px");
 test_valid_value("grid-auto-rows", "1px 2px 3px 0px");
 test_valid_value("grid-auto-rows", "fit-content(1px) minmax(2px, 3px) 4px");
 </script>