Align prefers-color-scheme:no-preference tests with spec.

The 'no-preference' value has been removed from the spec per resolution
in [1].

[1] w3c/csswg-drafts#3857 (comment)

Bug: 1091806
Change-Id: Id5fd41b93f14c7ee60d10aa4dae036558271c948
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2232924
Reviewed-by: Anders Hartvoll Ruud <[email protected]>
Commit-Queue: Rune Lillesveen <[email protected]>
Cr-Commit-Position: refs/heads/master@{#775910}

css/mediaqueries/prefers-color-scheme.html

@@ -6,7 +6,6 @@
 <script type="text/javascript" src="resources/matchmedia-utils.js"></script>
 <script>
 query_should_be_css_parseable("(prefers-color-scheme)");
-query_should_be_css_parseable("(prefers-color-scheme: no-preference)");
 query_should_be_css_parseable("(prefers-color-scheme: light)");
 query_should_be_css_parseable("(prefers-color-scheme: dark)");
 
@@ -16,9 +15,9 @@
 query_should_not_be_css_parseable("(prefers-color-scheme: dark 0)");
 query_should_not_be_css_parseable("(prefers-color-scheme: dark light)");
 query_should_not_be_css_parseable("(prefers-color-scheme: light/dark)");
+query_should_not_be_css_parseable("(prefers-color-scheme: no-preference)");
 
 query_should_be_js_parseable("(prefers-color-scheme)");
-query_should_be_js_parseable("(prefers-color-scheme: no-preference)");
 query_should_be_js_parseable("(prefers-color-scheme: light)");
 query_should_be_js_parseable("(prefers-color-scheme: dark)");
 
@@ -28,10 +27,10 @@
 query_should_not_be_js_parseable("(prefers-color-scheme: dark 0)");
 query_should_not_be_js_parseable("(prefers-color-scheme: dark light)");
 query_should_not_be_js_parseable("(prefers-color-scheme: light/dark)");
+query_should_not_be_js_parseable("(prefers-color-scheme: no-preference)");
 
 test(() => {
   let booleanContext = window.matchMedia("(prefers-color-scheme)");
-  let noPreference = window.matchMedia("(prefers-color-scheme: no-preference)");
-  assert_equals(booleanContext.matches, !noPreference.matches);
-}, "Check that no-preference evaluates to false in the boolean context");
+  assert_true(booleanContext.matches);
+}, "Check that prefer-color-scheme evaluates to true in the boolean context");
 </script>