findAndUpdate uses predicate, just add callback to update method

src/matrix/room/timeline/Timeline.js

@@ -122,7 +122,7 @@ export class Timeline {
         for (const entry of entries) {
             // this will use the comparator and thus
             // check for equality using the compare method in BaseEntry
-            this._remoteEntries.findAndUpdate(entry, (previousEntry, entry) => {
+            this._remoteEntries.update(entry, null, previousEntry => {
                 entry.transferLocalEchoState(previousEntry);
             });
         }

src/observable/list/SortedArray.js

@@ -57,9 +57,13 @@ export class SortedArray extends BaseObservableList {
         return false;
     }
 
-    update(item, updateParams = null) {
+    update(item, updateParams = null, previousCallback = null) {
         const idx = this.indexOf(item);
         if (idx !== -1) {
+            if (previousCallback) {
+                const oldItem = this._items[idx];
+                previousCallback(oldItem);
+            }
             this._items[idx] = item;
             this.emitUpdate(idx, item, updateParams);
         }