Issue #21686: Stop using internally stored tabs list in adapters

app/src/main/java/org/mozilla/fenix/tabstray/browser/BrowserTabsAdapter.kt

@@ -106,16 +106,14 @@ class BrowserTabsAdapter(
      * display itself.
      */
     override fun onBindViewHolder(holder: AbstractBrowserTabViewHolder, position: Int, payloads: List<Any>) {
-        val tabs = tabs ?: return
-
-        if (tabs.list.isEmpty()) return
+        if (currentList.isEmpty()) return
 
         if (payloads.isEmpty()) {
             onBindViewHolder(holder, position)
             return
         }
 
-        if (position == tabs.selectedIndex) {
+        if (position == selectedIndex) {
             if (payloads.contains(PAYLOAD_HIGHLIGHT_SELECTED_ITEM)) {
                 holder.updateSelectedTabIndicator(true)
             } else if (payloads.contains(PAYLOAD_DONT_HIGHLIGHT_SELECTED_ITEM)) {

app/src/main/java/org/mozilla/fenix/tabstray/browser/TabsAdapter.kt

@@ -30,12 +30,12 @@ abstract class TabsAdapter<T : TabViewHolder>(
     delegate: Observable<TabsTray.Observer> = ObserverRegistry()
 ) : ListAdapter<Tab, T>(DiffCallback), TabsTray, Observable<TabsTray.Observer> by delegate {
 
-    protected var tabs: Tabs? = null
+    protected var selectedIndex: Int? = null
     protected var styling: TabsTrayStyling = TabsTrayStyling()
 
     @CallSuper
     override fun updateTabs(tabs: Tabs) {
-        this.tabs = tabs
+        this.selectedIndex = tabs.selectedIndex
 
         submitList(tabs.list)
 
@@ -44,13 +44,10 @@ abstract class TabsAdapter<T : TabViewHolder>(
 
     @CallSuper
     override fun onBindViewHolder(holder: T, position: Int) {
-        val tabs = tabs ?: return
-
-        holder.bind(tabs.list[position], isTabSelected(tabs, position), styling, this)
+        holder.bind(getItem(position), selectedIndex == position, styling, this)
     }
 
-    final override fun isTabSelected(tabs: Tabs, position: Int): Boolean =
-        tabs.selectedIndex == position
+    override fun isTabSelected(tabs: Tabs, position: Int): Boolean = false
 
     private object DiffCallback : DiffUtil.ItemCallback<Tab>() {
         override fun areItemsTheSame(oldItem: Tab, newItem: Tab): Boolean {