Bug 1658780 - Update the prefers-contrast media query to use the new more/less keywords r=emilio

Per the resolution here:
https://github.com/w3c/csswg-drafts/issues/2943#issuecomment-672994920

Differential Revision: https://phabricator.services.mozilla.com/D86848

layout/reftests/high-contrast/prefers-contrast-002.html

@@ -9,7 +9,7 @@
         width: 100px;
         height: 100px;
     }
-    @media (prefers-contrast: high) {
+    @media (prefers-contrast: more) {
         div {
             outline: 2px solid #000000;
         }

layout/style/nsMediaFeatures.cpp

@@ -281,7 +281,7 @@ StyleContrastPref Gecko_MediaFeatures_PrefersContrast(
   // https://github.com/w3c/csswg-drafts/issues/3856#issuecomment-642313572
   // https://github.com/w3c/csswg-drafts/issues/2943
   if (!!LookAndFeel::GetInt(LookAndFeel::IntID::UseAccessibilityTheme, 0)) {
-    return StyleContrastPref::High;
+    return StyleContrastPref::More;
   }
   return StyleContrastPref::NoPreference;
 }

layout/style/test/chrome/test_chrome_only_media_queries.html

@@ -74,9 +74,9 @@ expectParseable("(-moz-os-version: windows-win8)");
 expectParseable("(-moz-os-version: windows-win10)");
 expectNonParseable("(-moz-os-version: )");
 
-expectParseable("(prefers-contrast: low)")
+expectParseable("(prefers-contrast: more)")
 expectParseable("(prefers-contrast: forced)")
 expectParseable("(prefers-contrast: no-preference)")
-expectParseable("(prefers-contrast: high)");
+expectParseable("(prefers-contrast: less)");
 expectParseable("(prefers-contrast)")
 </script>

servo/components/style/gecko/media_features.rs

@@ -313,8 +313,8 @@ fn eval_prefers_reduced_motion(device: &Device, query_value: Option<PrefersReduc
 #[repr(u8)]
 #[allow(missing_docs)]
 enum PrefersContrast {
-    High,
-    Low,
+    More,
+    Less,
     NoPreference,
     Forced,
 }
@@ -326,12 +326,11 @@ enum PrefersContrast {
 #[derive(Clone, Copy, Debug, FromPrimitive, PartialEq)]
 #[repr(u8)]
 pub enum ContrastPref {
-    /// High contrast is prefered. Corresponds to an accessibility theme
+    /// More contrast is prefered. Corresponds to an accessibility theme
     /// being enabled or firefox forcing high contrast colors.
-    High,
-    /// Low contrast is prefered. Corresponds to the
-    /// browser.display.prefers_low_contrast pref being true.
-    Low,
+    More,
+    /// Low contrast is prefered.
+    Less,
     /// The default value if neither high or low contrast is enabled.
     NoPreference,
 }
@@ -344,8 +343,8 @@ fn eval_prefers_contrast(device: &Device, query_value: Option<PrefersContrast>)
     if let Some(query_value) = query_value {
         match query_value {
             PrefersContrast::Forced => forced_colors,
-            PrefersContrast::High => contrast_pref == ContrastPref::High,
-            PrefersContrast::Low => contrast_pref == ContrastPref::Low,
+            PrefersContrast::More => contrast_pref == ContrastPref::More,
+            PrefersContrast::Less => contrast_pref == ContrastPref::Less,
             PrefersContrast::NoPreference => contrast_pref == ContrastPref::NoPreference,
         }
     } else {

testing/web-platform/tests/css/mediaqueries/prefers-contrast.html

@@ -7,8 +7,8 @@
 <script>
 query_should_be_css_parseable("(prefers-contrast)");
 query_should_be_css_parseable("(prefers-contrast: no-preference)");
-query_should_be_css_parseable("(prefers-contrast: high)");
-query_should_be_css_parseable("(prefers-contrast: low)");
+query_should_be_css_parseable("(prefers-contrast: more)");
+query_should_be_css_parseable("(prefers-contrast: less)");
 query_should_be_css_parseable("(prefers-contrast: forced)");
 
 query_should_not_be_css_parseable("(prefers-contrast: increase)");
@@ -18,11 +18,13 @@ query_should_not_be_css_parseable("(prefers-contrast: forced low)");
 query_should_not_be_css_parseable("(prefers-contrast > increase)");
 query_should_not_be_css_parseable("(prefers-increased-contrast)");
 query_should_not_be_css_parseable("(prefers-decreased-contrast)");
+query_should_not_be_css_parseable("(prefers-contrast: high)");
+query_should_not_be_css_parseable("(prefers-contrast: low)");
 
 query_should_be_js_parseable("(prefers-contrast)");
 query_should_be_js_parseable("(prefers-contrast: no-preference)");
-query_should_be_js_parseable("(prefers-contrast: high)");
-query_should_be_js_parseable("(prefers-contrast: low)");
+query_should_be_js_parseable("(prefers-contrast: more)");
+query_should_be_js_parseable("(prefers-contrast: less)");
 query_should_be_js_parseable("(prefers-contrast: forced)");
 
 query_should_not_be_js_parseable("(prefers-contrast: increase)");
@@ -32,6 +34,8 @@ query_should_not_be_js_parseable("(prefers-contrast: forced low)");
 query_should_not_be_js_parseable("(prefers-contrast > increase)");
 query_should_not_be_js_parseable("(prefers-increased-contrast)");
 query_should_not_be_js_parseable("(prefers-decreased-contrast)");
+query_should_not_be_js_parseable("(prefers-contrast: high)");
+query_should_not_be_js_parseable("(prefers-contrast: low)");
 
 test(() => {
   // no-preference is the default and all other values evaluate to