Add serialization WPT for CSS comparison functions min/max on <length>

Note that the test failures are due to an existing bug crbug.com/1008146
that we fail to sort terms in a summation in the serialization. The bug
is orthogonal to the implementation of min/max.

Bug: 978682
Change-Id: I8384274e4af3833003eee7e131fa8b46741f820b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1827724
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700552}

third_party/blink/web_tests/external/wpt/css/css-values/minmax-length-serialize-expected.txt

+This is a testharness.js-based test.
+PASS e.style['letter-spacing'] = "min(1px)" should set the property value
+PASS e.style['letter-spacing'] = "min(1cm)" should set the property value
+PASS e.style['letter-spacing'] = "min(1mm)" should set the property value
+PASS e.style['letter-spacing'] = "min(1Q)" should set the property value
+PASS e.style['letter-spacing'] = "min(1in)" should set the property value
+PASS e.style['letter-spacing'] = "min(1pc)" should set the property value
+PASS e.style['letter-spacing'] = "min(1pt)" should set the property value
+PASS e.style['letter-spacing'] = "min(1em)" should set the property value
+PASS e.style['letter-spacing'] = "min(1ex)" should set the property value
+PASS e.style['letter-spacing'] = "min(1ch)" should set the property value
+PASS e.style['letter-spacing'] = "min(1rem)" should set the property value
+PASS e.style['letter-spacing'] = "min(1vh)" should set the property value
+PASS e.style['letter-spacing'] = "min(1vw)" should set the property value
+PASS e.style['letter-spacing'] = "min(1vmin)" should set the property value
+PASS e.style['letter-spacing'] = "min(1vmax)" should set the property value
+PASS e.style['letter-spacing'] = "max(1px)" should set the property value
+PASS e.style['letter-spacing'] = "max(1cm)" should set the property value
+PASS e.style['letter-spacing'] = "max(1mm)" should set the property value
+PASS e.style['letter-spacing'] = "max(1Q)" should set the property value
+PASS e.style['letter-spacing'] = "max(1in)" should set the property value
+PASS e.style['letter-spacing'] = "max(1pc)" should set the property value
+PASS e.style['letter-spacing'] = "max(1pt)" should set the property value
+PASS e.style['letter-spacing'] = "max(1em)" should set the property value
+PASS e.style['letter-spacing'] = "max(1ex)" should set the property value
+PASS e.style['letter-spacing'] = "max(1ch)" should set the property value
+PASS e.style['letter-spacing'] = "max(1rem)" should set the property value
+PASS e.style['letter-spacing'] = "max(1vh)" should set the property value
+PASS e.style['letter-spacing'] = "max(1vw)" should set the property value
+PASS e.style['letter-spacing'] = "max(1vmin)" should set the property value
+PASS e.style['letter-spacing'] = "max(1vmax)" should set the property value
+PASS e.style['letter-spacing'] = "min(10px, 20px, 30px)" should set the property value
+PASS e.style['letter-spacing'] = "min(30px, 20px, 10px)" should set the property value
+PASS e.style['letter-spacing'] = "min(20px, 1em, 10vw)" should set the property value
+PASS e.style['letter-spacing'] = "min(10vw, 1em, 20px)" should set the property value
+PASS e.style['letter-spacing'] = "max(10px, 20px, 30px)" should set the property value
+PASS e.style['letter-spacing'] = "max(30px, 20px, 10px)" should set the property value
+PASS e.style['letter-spacing'] = "max(20px, 1em, 10vw)" should set the property value
+PASS e.style['letter-spacing'] = "max(10vw, 1em, 20px)" should set the property value
+PASS e.style['letter-spacing'] = "calc(min(10px) + max(1em) + min(10vw))" should set the property value
+PASS e.style['letter-spacing'] = "calc(max(1em) + min(10vw) + max(10px))" should set the property value
+PASS e.style['letter-spacing'] = "calc(10px + min(1em))" should set the property value
+FAIL e.style['letter-spacing'] = "calc(min(1em) + 10px)" should set the property value assert_equals: serialization should be canonical expected "calc(10px + min(1em))" but got "calc(min(1em) + 10px)"
+PASS e.style['letter-spacing'] = "calc(10px + max(1em))" should set the property value
+FAIL e.style['letter-spacing'] = "calc(max(1em) + 10px)" should set the property value assert_equals: serialization should be canonical expected "calc(10px + max(1em))" but got "calc(max(1em) + 10px)"
+Harness: the test ran to completion.
+

third_party/blink/web_tests/external/wpt/css/css-values/minmax-length-serialize.html

+<!DOCTYPE html>
+<link rel="help" href="https://drafts.csswg.org/css-values-4/#comp-func">
+<link rel="help" href="https://drafts.csswg.org/css-values-4/#lengths">
+<link rel="help" href="https://drafts.csswg.org/css-values-4/#calc-serialize">
+<link rel="author" title="Xiaocheng Hu" href="mailto:xiaochengh@chromium.org">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../support/parsing-testcommon.js"></script>
+<script>
+const property = 'letter-spacing';
+
+function test_valid_length(value, expected) {
+  test_valid_value(property, value, expected);
+}
+
+test_valid_length('min(1px)', 'min(1px)');
+test_valid_length('min(1cm)', 'min(1cm)');
+test_valid_length('min(1mm)', 'min(1mm)');
+// Values are case-insensitive and serialize as lower case, for example 1Q
+// serializes as 1q.
+test_valid_length('min(1Q)', 'min(1q)');
+test_valid_length('min(1in)', 'min(1in)');
+test_valid_length('min(1pc)', 'min(1pc)');
+test_valid_length('min(1pt)', 'min(1pt)');
+test_valid_length('min(1em)', 'min(1em)');
+test_valid_length('min(1ex)', 'min(1ex)');
+test_valid_length('min(1ch)', 'min(1ch)');
+test_valid_length('min(1rem)', 'min(1rem)');
+test_valid_length('min(1vh)', 'min(1vh)');
+test_valid_length('min(1vw)', 'min(1vw)');
+test_valid_length('min(1vmin)', 'min(1vmin)');
+test_valid_length('min(1vmax)', 'min(1vmax)');
+test_valid_length('max(1px)', 'max(1px)');
+test_valid_length('max(1cm)', 'max(1cm)');
+test_valid_length('max(1mm)', 'max(1mm)');
+test_valid_length('max(1Q)', 'max(1q)');
+test_valid_length('max(1in)', 'max(1in)');
+test_valid_length('max(1pc)', 'max(1pc)');
+test_valid_length('max(1pt)', 'max(1pt)');
+test_valid_length('max(1em)', 'max(1em)');
+test_valid_length('max(1ex)', 'max(1ex)');
+test_valid_length('max(1ch)', 'max(1ch)');
+test_valid_length('max(1rem)', 'max(1rem)');
+test_valid_length('max(1vh)', 'max(1vh)');
+test_valid_length('max(1vw)', 'max(1vw)');
+test_valid_length('max(1vmin)', 'max(1vmin)');
+test_valid_length('max(1vmax)', 'max(1vmax)');
+
+test_valid_length('min(10px, 20px, 30px)', 'min(10px, 20px, 30px)');
+test_valid_length('min(30px, 20px, 10px)', 'min(30px, 20px, 10px)');
+test_valid_length('min(20px, 1em, 10vw)', 'min(20px, 1em, 10vw)');
+test_valid_length('min(10vw, 1em, 20px)', 'min(10vw, 1em, 20px)');
+test_valid_length('max(10px, 20px, 30px)', 'max(10px, 20px, 30px)');
+test_valid_length('max(30px, 20px, 10px)', 'max(30px, 20px, 10px)');
+test_valid_length('max(20px, 1em, 10vw)', 'max(20px, 1em, 10vw)');
+test_valid_length('max(10vw, 1em, 20px)', 'max(10vw, 1em, 20px)');
+
+test_valid_length('calc(min(10px) + max(1em) + min(10vw))', 'calc(min(10px) + max(1em) + min(10vw))');
+test_valid_length('calc(max(1em) + min(10vw) + max(10px))', 'calc(max(1em) + min(10vw) + max(10px))');
+test_valid_length('calc(10px + min(1em))', 'calc(10px + min(1em))');
+test_valid_length('calc(min(1em) + 10px)', 'calc(10px + min(1em))');
+test_valid_length('calc(10px + max(1em))', 'calc(10px + max(1em))');
+test_valid_length('calc(max(1em) + 10px)', 'calc(10px + max(1em))');
+
+</script>