[@container] Keep duplicate container names in computed value

Per resolution [1], don't remove duplicate container names from the
computed value.

[1] w3c/csswg-drafts#7181

Bug: 1145970
Change-Id: I3950c9dafefe952cbbe90cec4e1df09d8e9382e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3663167
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1007289}

css/css-contain/container-queries/container-name-computed.html

@@ -16,8 +16,8 @@
 test_computed_value('container-name', 'FoO');
 test_computed_value('container-name', 'foo bar');
 test_computed_value('container-name', 'bar foo');
-test_computed_value('container-name', 'foo foo bar', 'foo bar');
-test_computed_value('container-name', 'foo bar foo', 'foo bar');
-test_computed_value('container-name', 'bar foo foo', 'bar foo');
+test_computed_value('container-name', 'foo foo bar');
+test_computed_value('container-name', 'foo bar foo');
+test_computed_value('container-name', 'bar foo foo');
 test_computed_value('container-name', '\\!escaped');
 </script>