Bug 1539326 - Cherry-pick changes for servo/servo#8539 (config preferences backend restructure). r=npotb

servo/components/style/global_style_data.rs

@@ -66,11 +66,11 @@ lazy_static! {
             Ok(num) => num,
             #[cfg(feature = "servo")]
             _ => {
+                use servo_config::pref;
                 // We always set this pref on startup, before layout or script
                 // have had a chance of accessing (and thus creating) the
                 // thread-pool.
-                use servo_config::prefs::PREFS;
-                PREFS.get("layout.threads").as_u64().unwrap() as usize
+                pref!(layout.threads) as usize
             }
             #[cfg(feature = "gecko")]
             _ => {

servo/components/style/properties/properties.mako.rs

@@ -33,7 +33,7 @@ use crate::parser::ParserContext;
 use crate::properties::longhands::system_font::SystemFont;
 use crate::selector_parser::PseudoElement;
 use selectors::parser::SelectorParseErrorKind;
-#[cfg(feature = "servo")] use servo_config::prefs::PREFS;
+#[cfg(feature = "servo")] use servo_config::prefs;
 use style_traits::{CssWriter, KeywordsCollectFn, ParseError, ParsingMode};
 use style_traits::{SpecifiedValueInfo, StyleParseErrorKind, ToCss};
 use crate::stylesheets::{CssRuleType, Origin, UrlExtraData};
@@ -515,7 +515,7 @@ impl NonCustomPropertyId {
                     Some(pref) => pref,
                 };
 
-                PREFS.get(pref).as_boolean().unwrap_or(false)
+                prefs::pref_map().get(pref).as_bool().unwrap_or(false)
             % else:
                 unsafe { structs::nsCSSProps_gPropertyEnabled[self.0] }
             % endif

servo/components/style/stylesheets/viewport_rule.rs

@@ -38,11 +38,8 @@ use style_traits::{CssWriter, ParseError, PinchZoomFactor, StyleParseErrorKind,
 /// Whether parsing and processing of `@viewport` rules is enabled.
 #[cfg(feature = "servo")]
 pub fn enabled() -> bool {
-    use servo_config::prefs::PREFS;
-    PREFS
-        .get("layout.viewport.enabled")
-        .as_boolean()
-        .unwrap_or(false)
+    use servo_config::pref;
+    pref!(layout.viewport.enabled)
 }
 
 /// Whether parsing and processing of `@viewport` rules is enabled.