Refactor Zen tab management to improve performance and enable conditional functionality

src/browser/base/content/zen-styles/zen-tabs/vertical-tabs.css

@@ -184,8 +184,6 @@
 
   #vertical-pinned-tabs-container {
     padding-inline-end: 0 !important;
-    max-height: unset !important;
-    overflow: visible !important;
     display: flex !important;
     flex-direction: column;
 

src/browser/base/zen-components/ZenPinnedTabManager.mjs

@@ -39,6 +39,9 @@
   class ZenPinnedTabManager extends ZenPreloadedFeature {
 
     init() {
+      if (!this.enabled) {
+        return;
+      }
       this.observer = new ZenPinnedTabsObserver();
       this._initClosePinnedTabShortcut();
       this._insertItemsIntoTabContextMenu();
@@ -48,9 +51,23 @@
     }
 
     async initTabs() {
+      if (!this.enabled) {
+        return;
+      }
       await ZenPinnedTabsStorage.init();
     }
 
+    get enabled() {
+      if (!this._enabled) {
+        this._enabled = !(
+          docElement.hasAttribute('privatebrowsingmode') ||
+          docElement.getAttribute('chromehidden').includes('toolbar') ||
+          docElement.getAttribute('chromehidden').includes('menubar')
+        );
+      }
+      return this._enabled;
+    }
+
     async _refreshPinnedTabs() {
       await this._initializePinsCache();
       this._initializePinnedTabs();
@@ -161,6 +178,7 @@
     }
 
     _onPinnedTabEvent(action, event) {
+      if (!this.enabled) return;
       const tab = event.target;
       switch (action) {
         case "TabPinned":
@@ -449,6 +467,9 @@
     }
 
     updatePinnedTabContextMenu(contextTab) {
+      if (!this.enabled) {
+        return;
+      }
       const isVisible = contextTab.pinned  && !contextTab.multiselected;
       document.getElementById("context_zen-reset-pinned-tab").hidden = !isVisible || !contextTab.getAttribute("zen-pin-id");
       document.getElementById("context_zen-replace-pinned-url-with-current").hidden = !isVisible;

src/browser/base/zen-components/ZenTabUnloader.mjs

@@ -250,7 +250,7 @@
 
     canUnloadTab(tab, currentTimestamp, excludedUrls, ignoreTimestamp = false) {
       if (
-        tab.pinned ||
+        (tab.pinned && !ignoreTimestamp) ||
         tab.selected ||
         tab.multiselected ||
         tab.hasAttribute('busy') ||
@@ -259,9 +259,9 @@
         tab.splitView ||
         tab.attention ||
         tab.linkedBrowser?.zenModeActive ||
-        tab.pictureinpicture ||
+        (tab.pictureinpicture && !ignoreTimestamp) ||
-        tab.soundPlaying ||
+        (tab.soundPlaying && !ignoreTimestamp) ||
-        tab.zenIgnoreUnload ||
+        (tab.zenIgnoreUnload && !ignoreTimestamp) ||
         excludedUrls.some((url) => url.test(tab.linkedBrowser.currentURI.spec))
       ) {
         return false;