fix: Make sure to save the state of the last restored 'normal' window, b=no-bug, c=no-component

src/browser/components/sessionstore/SessionStore-sys-mjs.patch

@@ -1,5 +1,5 @@
 diff --git a/browser/components/sessionstore/SessionStore.sys.mjs b/browser/components/sessionstore/SessionStore.sys.mjs
-index 2a055f0c5f34f0a2667f659185120c07d38f4e41..cd350d9e787c1ef0d1dffcb7d872b9c2e8fe19ff 100644
+index 2a055f0c5f34f0a2667f659185120c07d38f4e41..5b16b12fb02799b12543294a9fccceef47067d53 100644
 --- a/browser/components/sessionstore/SessionStore.sys.mjs
 +++ b/browser/components/sessionstore/SessionStore.sys.mjs
 @@ -127,6 +127,9 @@ const TAB_EVENTS = [
@@ -95,15 +95,26 @@ index 2a055f0c5f34f0a2667f659185120c07d38f4e41..cd350d9e787c1ef0d1dffcb7d872b9c2
  
      TAB_EVENTS.forEach(function (aEvent) {
        tabbrowser.tabContainer.removeEventListener(aEvent, this, true);
-@@ -2491,7 +2509,7 @@ var SessionStoreInternal = {
+@@ -2434,7 +2452,7 @@ var SessionStoreInternal = {
+ 
+       let isLastRegularWindow =
+         Object.values(this._windows).filter(
+-          wData => !wData.isPrivate && !wData.isTaskbarTab
++          wData => !wData.isPrivate && !wData.isTaskbarTab && !wData.isZenUnsynced
+         ).length == 1;
+       this._log.debug(
+         `onClose, closing window isLastRegularWindow? ${isLastRegularWindow}`
+@@ -2491,8 +2509,8 @@ var SessionStoreInternal = {
        // 2) Flush the window.
        // 3) When the flush is complete, revisit our decision to store the window
        //    in _closedWindows, and add/remove as necessary.
 -      if (!winData.isPrivate && !winData.isTaskbarTab) {
+-        this.maybeSaveClosedWindow(winData, isLastWindow);
 +      if (!winData.isPrivate && !winData.isTaskbarTab && !winData.isZenUnsynced) {
-         this.maybeSaveClosedWindow(winData, isLastWindow);
++        this.maybeSaveClosedWindow(winData, isLastWindow, isLastRegularWindow);
        }
  
+       completionPromise = lazy.TabStateFlusher.flushWindow(aWindow).then(() => {
 @@ -2512,7 +2530,8 @@ var SessionStoreInternal = {
  
          // Save non-private windows if they have at
@@ -114,11 +125,20 @@ index 2a055f0c5f34f0a2667f659185120c07d38f4e41..cd350d9e787c1ef0d1dffcb7d872b9c2
            this.maybeSaveClosedWindow(winData, isLastWindow);
  
            if (!isLastWindow && winData.closedId > -1) {
+@@ -2589,7 +2608,7 @@ var SessionStoreInternal = {
+    *        to call this method again asynchronously (for example, after
+    *        a window flush).
+    */
+-  maybeSaveClosedWindow(winData, isLastWindow) {
++  maybeSaveClosedWindow(winData, isLastWindow, isLastRegularWindow = false) {
+     // Make sure SessionStore is still running, and make sure that we
+     // haven't chosen to forget this window.
+     if (
 @@ -2608,6 +2627,9 @@ var SessionStoreInternal = {
        let alreadyStored = winIndex != -1;
        // If sidebar command is truthy, i.e. sidebar is open, store sidebar settings
        let shouldStore = hasSaveableTabs || isLastWindow;
-+      lazy.ZenSessionStore.maybeSaveClosedWindow(winData, isLastWindow);
++      lazy.ZenSessionStore.maybeSaveClosedWindow(winData, isLastRegularWindow);
 +      // TODO: Do we want to store closed Zen windows? All of them are synced anyways
 +      shouldStore = false;
  

src/zen/sessionstore/ZenWindowSync.sys.mjs

@@ -577,7 +577,7 @@ class nsZenWindowSync {
    * @param {object} aOtherTab - The tab in the other window.
    */
   async #swapBrowserDocShellsAsync(aOurTab, aOtherTab) {
-    let promise = this.#maybeFlushTabState(aOurTab);
+    let promise = this.#maybeFlushTabState(aOtherTab);
     await this.#styleSwapedBrowsers(
       aOurTab,
       aOtherTab,
@@ -644,13 +644,23 @@ class nsZenWindowSync {
     // See https://github.com/zen-browser/desktop/issues/11851, swapping the browsers
     // don't seem to update the state's cache properly, leading to issues when restoring
     // the session later on.
-    let tabStateEntries = this.#getTabEntriesFromCache(aOurTab);
+    let tabStateEntries = this.#getTabEntriesFromCache(aOtherTab);
+    const setStateToTab = () => {
+      if (!tabStateEntries?.entries.length) {
+        this.log(`Error: No tab state entries found for tab ${aOurTab.id} during swap`);
+        return;
+      }
+      lazy.TabStateCache.update(aOurTab.linkedBrowser.permanentKey, {
+        history: tabStateEntries,
+      });
+    };
     // Running `swapBrowsersAndCloseOther` doesn't expect us to use the tab after
     // the operation, so it doesn't really care about cleaning up the other tab.
     // We need to make a new tab progress listener for the other tab after the swap.
     this.#withRestoreTabProgressListener(
       aOtherTab,
       () => {
+        setStateToTab();
         this.log(`Swapping docshells between windows for tab ${aOurTab.id}`);
         aOurTab.ownerGlobal.gBrowser.swapBrowsersAndCloseOther(aOurTab, aOtherTab, false);
         // Since we are moving progress listeners around, there's a chance that we
@@ -701,13 +711,7 @@ class nsZenWindowSync {
     // we would start receiving invalid history changes from the the incorrect
     // browser view that was just swapped out.
     return this.#maybeFlushTabState(aOurTab).finally(() => {
-      if (!tabStateEntries?.entries.length) {
-        this.log(`Error: No tab state entries found for tab ${aOtherTab.id} during swap`);
-        return;
-      }
-      lazy.TabStateCache.update(aOurTab.linkedBrowser.permanentKey, {
-        history: tabStateEntries,
-      });
+      setStateToTab();
     });
   }
 
@@ -905,7 +909,7 @@ class nsZenWindowSync {
     if (aTab.linkedBrowser) {
       cachedState = lazy.TabStateCache.get(aTab.linkedBrowser.permanentKey);
     }
-    return cachedState?.history?.entries ? cachedState.history : { entries: [] };
+    return cachedState?.history?.entries ? Cu.cloneInto(cachedState.history, {}) : { entries: [] };
   }
 
   /**