Let static prefs default to style_config's prefs (#306)

This will allow Servo to enable them e.g. when turning on experimental
features (`--enable-experimental-web-platform-features`), or when
running specific tests.

Servo PR: servo/servo#42410

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

Author: Loirooriol

README.md

@@ -93,8 +93,8 @@ stylo_traits = { path = "../stylo/style_traits" }
 Releases are made every time this repository rebases its changes on top of the latest version of upstream Stylo. There are a lot of crates here. In order to publish them, they must be done in order. One order that works is:
 
 - selectors
-- stylo_static_prefs
 - stylo_config
+- stylo_static_prefs
 - stylo_atoms
 - stylo_malloc_size_of
 - stylo_dom

stylo_static_prefs/Cargo.toml

@@ -9,3 +9,6 @@ keywords = ["css", "style"]
 license = "MPL-2.0"
 edition = "2021"
 readme = "../README.md"
+
+[dependencies]
+style_config = { workspace = true }

stylo_static_prefs/src/lib.rs

@@ -52,6 +52,6 @@ macro_rules! pref {
         true
     };
     ($string:literal) => {
-        false
+        style_config::get_bool($string);
     };
 }