Fixing regression in background task loading.

Bug: 117603579
Test: Take systrace, ensure that we aren't loading thumbnails on the UI
      thread

Change-Id: I4b522246a5ab12dc37c1dffdccd05232bbc1f6fe
diff --git a/quickstep/src/com/android/quickstep/RecentsModel.java b/quickstep/src/com/android/quickstep/RecentsModel.java
index e184a9b..2e4d4d2 100644
--- a/quickstep/src/com/android/quickstep/RecentsModel.java
+++ b/quickstep/src/com/android/quickstep/RecentsModel.java
@@ -143,8 +143,8 @@
         }
 
         // Keep the cache up to date with the latest thumbnails
+        int runningTaskId = RecentsModel.getRunningTaskId();
         mTaskList.getTasks(mThumbnailCache.getCacheSize(), true /* keysOnly */, (tasks) -> {
-            int runningTaskId = RecentsModel.getRunningTaskId();
             for (Task task : tasks) {
                 if (task.key.id == runningTaskId) {
                     // Skip the running task, it's not going to have an up-to-date snapshot by the
diff --git a/quickstep/src/com/android/quickstep/TaskThumbnailCache.java b/quickstep/src/com/android/quickstep/TaskThumbnailCache.java
index c47101b..61a191f 100644
--- a/quickstep/src/com/android/quickstep/TaskThumbnailCache.java
+++ b/quickstep/src/com/android/quickstep/TaskThumbnailCache.java
@@ -108,8 +108,9 @@
         Preconditions.assertUIThread();
 
         // Fetch the thumbnail for this task and put it in the cache
-        mCache.put(task.key, ActivityManagerWrapper.getInstance().getTaskThumbnail(
-                task.key.id, true /* reducedResolution */));
+        updateThumbnailInBackground(task, true /* reducedResolution */, (t) -> {
+            mCache.put(task.key, t.thumbnail);
+        });
     }