Synchronize bubble activity rendering status and its visibility change.

- Add an API ITaskStackListener.onSingleTaskDisplayDrawn() to notifity contents
  are drawn for the first time on a display which can only contain one task.
- BubbleController updates contents visibility (actually alpha value) of
  the Surface in a ActivityView.

Bug: 130442248
Test: atest WmTests:TaskStackChangedListenerTest
Change-Id: Ie5aed373996419b059935889b564ca91c2e3cf23
diff --git a/services/core/java/com/android/server/wm/AppTransitionController.java b/services/core/java/com/android/server/wm/AppTransitionController.java
index d4c4e6a..6c5ef52 100644
--- a/services/core/java/com/android/server/wm/AppTransitionController.java
+++ b/services/core/java/com/android/server/wm/AppTransitionController.java
@@ -28,6 +28,7 @@
 import static android.view.WindowManager.TRANSIT_KEYGUARD_GOING_AWAY;
 import static android.view.WindowManager.TRANSIT_KEYGUARD_GOING_AWAY_ON_WALLPAPER;
 import static android.view.WindowManager.TRANSIT_NONE;
+import static android.view.WindowManager.TRANSIT_SHOW_SINGLE_TASK_DISPLAY;
 import static android.view.WindowManager.TRANSIT_TASK_CLOSE;
 import static android.view.WindowManager.TRANSIT_TASK_IN_PLACE;
 import static android.view.WindowManager.TRANSIT_TASK_OPEN;
@@ -211,6 +212,12 @@
         mService.mAtmInternal.notifyAppTransitionStarting(mTempTransitionReasons.clone(),
                 SystemClock.uptimeMillis());
 
+        if (transit == TRANSIT_SHOW_SINGLE_TASK_DISPLAY) {
+            mService.mAnimator.addAfterPrepareSurfacesRunnable(() -> {
+                mService.mAtmInternal.notifySingleTaskDisplayDrawn(mDisplayContent.getDisplayId());
+            });
+        }
+
         Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
 
         mDisplayContent.pendingLayoutChanges |=