Auto merge of #11338 - Ms2ger:compositor-refcell, r=nox

Take ScriptThread::compositor out of its RefCell.

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 --faster` 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 refactoring

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

There's no reason for it; IpcSender::send takes &self.

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components/script/dom/document.rs

@@ -1055,7 +1055,7 @@ impl Document {
                               key: Key,
                               state: KeyState,
                               modifiers: KeyModifiers,
-                              compositor: &mut IpcSender<ScriptToCompositorMsg>) {
+                              compositor: &IpcSender<ScriptToCompositorMsg>) {
         let focused = self.get_focused_element();
         let body = self.GetBody();