Auto merge of #12178 - frewsxcv:prefs, r=emilio

Refactor `util::prefs` operations to be methods on static struct.

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="35" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/12178)
<!-- Reviewable:end -->

1 files changed, 3 insertions, 3 deletions

diff --git a/components/script/dom/htmliframeelement.rs b/components/script/dom/htmliframeelement.rs
index 2c71488c5dc..f1f3c0e29de 100644
--- a/components/script/dom/htmliframeelement.rs
+++ b/components/script/dom/htmliframeelement.rs
@@ -48,7 +48,7 @@ use string_cache::Atom;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto};
 use style::context::ReflowGoal;
 use url::Url;
-use util::prefs::mozbrowser_enabled;
+use util::prefs::PREFS;
 use util::servo_version;
 
 bitflags! {
@@ -145,7 +145,7 @@ impl HTMLIFrameElement {
               .send(ConstellationMsg::ScriptLoadedURLInIFrame(load_info))
               .unwrap();
 
-        if mozbrowser_enabled() {
+        if PREFS.is_mozbrowser_enabled() {
             // https://developer.mozilla.org/en-US/docs/Web/Events/mozbrowserloadstart
             self.dispatch_mozbrowser_event(MozBrowserEvent::LoadStart);
         }
@@ -164,7 +164,7 @@ impl HTMLIFrameElement {
         // TODO(gw): Support mozbrowser event types that have detail which is not a string.
         // See https://developer.mozilla.org/en-US/docs/Web/API/Using_the_Browser_API
         // for a list of mozbrowser events.
-        assert!(mozbrowser_enabled());
+        assert!(PREFS.is_mozbrowser_enabled());
 
         if self.Mozbrowser() {
             let window = window_from_node(self);