Only update the task description when the task/description changes

- Instead of updating again for every task when we fetch recents, only update
  when the activities change

Bug: 69166452
Test: android.app.cts.TaskDescriptionTest
Change-Id: Idb66ee4c3ca6f637b6ab52c6d52dd1a09926c48f

services/core/java/com/android/server/am/RecentTasks.java

@@ -1426,9 +1426,6 @@ class RecentTasks {
      * Creates a new RecentTaskInfo from a TaskRecord.
      */
     ActivityManager.RecentTaskInfo createRecentTaskInfo(TaskRecord tr) {
-        // Update the task description to reflect any changes in the task stack
-        tr.updateTaskDescription();
-
         // Compose the recent task info
         ActivityManager.RecentTaskInfo rti = new ActivityManager.RecentTaskInfo();
         rti.id = tr.getTopActivity() == null ? INVALID_TASK_ID : tr.taskId;

services/core/java/com/android/server/am/TaskRecord.java

@@ -1616,6 +1616,9 @@ class TaskRecord extends ConfigurationContainer implements TaskWindowContainerLi
         final int effectiveRootIndex = findEffectiveRootIndex();
         final ActivityRecord r = mActivities.get(effectiveRootIndex);
         setIntent(r);
+
+        // Update the task description when the activities change
+        updateTaskDescription();
     }
 
     void saveToXml(XmlSerializer out) throws IOException, XmlPullParserException {