From afbdf6822c9e9f9b6d44b9ea6904cb10878126b1 Mon Sep 17 00:00:00 2001
From: Nika Layzell <nika@thelayzells.com>
Date: Thu, 21 Mar 2024 19:35:40 +0000
Subject: [PATCH] Bug 1886852 - Avoid registering unnecessary MessageManager
 listeners when SHIP is enabled, r=smaug!

Differential Revision: https://phabricator.services.mozilla.com/D205377
---
 .../sessionstore/SessionStore.sys.mjs         | 27 ++++++++++++-------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/browser/components/sessionstore/SessionStore.sys.mjs b/browser/components/sessionstore/SessionStore.sys.mjs
index f078708dd3e7a..cd2c397e09a7e 100644
--- a/browser/components/sessionstore/SessionStore.sys.mjs
+++ b/browser/components/sessionstore/SessionStore.sys.mjs
@@ -1730,6 +1730,13 @@ var SessionStoreInternal = {
    * and thus enables communication with OOP tabs.
    */
   receiveMessage(aMessage) {
+    if (Services.appinfo.sessionHistoryInParent) {
+      throw new Error(
+        `received unexpected message '${aMessage.name}' with ` +
+          `sessionHistoryInParent enabled`
+      );
+    }
+
     // If we got here, that means we're dealing with a frame message
     // manager message, so the target will be a <xul:browser>.
     var browser = aMessage.target;
@@ -1910,14 +1917,14 @@ var SessionStoreInternal = {
     // internal data about the window.
     aWindow.__SSi = this._generateWindowID();
 
-    let mm = aWindow.getGroupMessageManager("browsers");
-    MESSAGES.forEach(msg => {
-      let listenWhenClosed = CLOSED_MESSAGES.has(msg);
-      mm.addMessageListener(msg, this, listenWhenClosed);
-    });
-
-    // Load the frame script after registering listeners.
     if (!Services.appinfo.sessionHistoryInParent) {
+      let mm = aWindow.getGroupMessageManager("browsers");
+      MESSAGES.forEach(msg => {
+        let listenWhenClosed = CLOSED_MESSAGES.has(msg);
+        mm.addMessageListener(msg, this, listenWhenClosed);
+      });
+
+      // Load the frame script after registering listeners.
       mm.loadFrameScript(
         "chrome://browser/content/content-sessionStore.js",
         true,
@@ -2395,8 +2402,10 @@ var SessionStoreInternal = {
     // Cache the window state until it is completely gone.
     DyingWindowCache.set(aWindow, winData);
 
-    let mm = aWindow.getGroupMessageManager("browsers");
-    MESSAGES.forEach(msg => mm.removeMessageListener(msg, this));
+    if (!Services.appinfo.sessionHistoryInParent) {
+      let mm = aWindow.getGroupMessageManager("browsers");
+      MESSAGES.forEach(msg => mm.removeMessageListener(msg, this));
+    }
 
     this._saveableClosedWindowData.delete(winData);
     delete aWindow.__SSi;