1 files changed, 29 insertions, 0 deletions
diff --git a/browser/actors/RFPHelperChild.jsm b/browser/actors/RFPHelperChild.jsm
new file mode 100644
index 0000000000..907197aeec
--- /dev/null
+++ b/browser/actors/RFPHelperChild.jsm
@@ -0,0 +1,29 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+var EXPORTED_SYMBOLS = ["RFPHelperChild"];
+
+const { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+const kPrefLetterboxing = "privacy.resistFingerprinting.letterboxing";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "isLetterboxingEnabled",
+  kPrefLetterboxing,
+  false
+);
+
+class RFPHelperChild extends JSWindowActorChild {
+  handleEvent(event) {
+    if (lazy.isLetterboxingEnabled && event.type == "resize") {
+      this.sendAsyncMessage("Letterboxing:ContentSizeUpdated");
+    }
+  }
+}