Auto merge of #23253 - BartGitHub:refactor-promise-compartment, r=jdm

Refactor promise compartment

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This PR adds a mechanism to verify that certain code is executed inside a ```JSAutoCompartment```, and applies this to the ```Promise::new_in_current_compartment``` constructor.

r? @jdm

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- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23167

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- [x] These changes do not require tests because they do not change existing functionality.

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1 files changed, 34 insertions, 0 deletions

diff --git a/components/script/compartments.rs b/components/script/compartments.rs
new file mode 100644
index 00000000000..aedabca773e
--- /dev/null
+++ b/components/script/compartments.rs
@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use crate::dom::globalscope::GlobalScope;
+use js::jsapi::{GetCurrentRealmOrNull, JSAutoCompartment};
+
+pub struct AlreadyInCompartment(());
+
+impl AlreadyInCompartment {
+    #![allow(unsafe_code)]
+    pub fn assert(global: &GlobalScope) -> AlreadyInCompartment {
+        unsafe {
+            assert!(!GetCurrentRealmOrNull(global.get_cx()).is_null());
+        }
+        AlreadyInCompartment(())
+    }
+}
+
+#[derive(Clone, Copy)]
+pub enum InCompartment<'a> {
+    Already(&'a AlreadyInCompartment),
+    Entered(&'a JSAutoCompartment),
+}
+
+impl<'a> InCompartment<'a> {
+    pub fn in_compartment(token: &AlreadyInCompartment) -> InCompartment {
+        InCompartment::Already(token)
+    }
+
+    pub fn entered(token: &JSAutoCompartment) -> InCompartment {
+        InCompartment::Entered(token)
+    }
+}