Add proof that code is executed in compartment

components/script/compartments.rs

@@ -0,0 +1,33 @@
+/* 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(())
+    }
+}
+
+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)
+    }
+}

components/script/lib.rs

@@ -57,6 +57,7 @@ mod devtools;
 pub mod document_loader;
 #[macro_use]
 mod dom;
+mod compartments;
 pub mod fetch;
 mod image_listener;
 mod layout_image;