[@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}
NOKEYCHECK=True
GitOrigin-RevId: d793fb60b8ba4f9a2270a6b7879100d9953da807

blink/renderer/core/css/resolver/style_builder_converter.cc

@@ -2292,20 +2292,15 @@ ScrollbarGutter StyleBuilderConverter::ConvertScrollbarGutter(
 Vector<AtomicString> StyleBuilderConverter::ConvertContainerName(
     StyleResolverState& state,
     const CSSValue& value) {
-  HashSet<AtomicString> seen;
   Vector<AtomicString> names;
 
   if (auto* ident = DynamicTo<CSSIdentifierValue>(value)) {
     DCHECK_EQ(To<CSSIdentifierValue>(value).GetValueID(), CSSValueID::kNone);
     return names;
   }
 
-  for (const auto& item : To<CSSValueList>(value)) {
-    const AtomicString& value = To<CSSCustomIdentValue>(item.Get())->Value();
-    if (!seen.insert(value).is_new_entry)
-      continue;
-    names.push_back(value);
-  }
+  for (const auto& item : To<CSSValueList>(value))
+    names.push_back(To<CSSCustomIdentValue>(item.Get())->Value());
 
   return names;
 }

blink/web_tests/external/wpt/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>