devtools: Allow registering environment actor from debugger.js (#43166)

This functionality will be used in a follow up patch to implement the
getEnvironment message.

Testing: Check `mach test-devtools` and manual test
Part of: #36027

Signed-off-by: eri <eri@igalia.com>
Co-authored-by: atbrakhi <atbrakhi@igalia.com>

components/script_bindings/webidls/DebuggerGetEnvironmentEvent.webidl

@@ -0,0 +1,18 @@
+/* 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/. */
+
+// This interface is entirely internal to Servo, and should not be accessible to
+// web pages.
+partial interface DebuggerGlobalScope {
+    DOMString? registerEnvironmentActor(
+        EnvironmentInfo result,
+        DOMString? parent
+    );
+};
+
+dictionary EnvironmentInfo {
+    DOMString type_;
+    DOMString scopeKind;
+    DOMString functionDisplayName;
+};