Fix some visibility issues with tasks & task overlays

- Make the overlay host surface visibility mirror the actual visibility
  of the task.  Currently WM may show the task surface prior to any
  children being shown, which can lead to a flash of the overlay when
  launching tasks
- Also prevent the task visibilty from being clobbered by the Shell when
  a task changes windowing modes.  The task visibility is updated by WM
  in Task#prepareSurfaces(), but the Shell will still try to show the
  task surface in the WCT transaction callback

Bug: 255777383
Test: Launch game with existing visible task overlay
Test: Split app that shows a task overlay (ie. game dashboard button), then
      dismiss split
Change-Id: I950df0d88a56617369e6c15f66268455fd52d8b4

libs/WindowManager/Shell/src/com/android/wm/shell/fullscreen/FullscreenTaskListener.java

@@ -114,7 +114,9 @@ public class FullscreenTaskListener implements ShellTaskOrganizer.TaskListener {
                 t.setPosition(leash, positionInParent.x, positionInParent.y);
                 t.setAlpha(leash, 1f);
                 t.setMatrix(leash, 1, 0, 0, 1);
-                t.show(leash);
+                if (taskInfo.isVisible) {
+                    t.show(leash);
+                }
             });
         }
     }

services/core/java/com/android/server/wm/Task.java

@@ -3327,12 +3327,17 @@ class Task extends TaskFragment {
         // We intend to let organizer manage task visibility but it doesn't
         // have enough information until we finish shell transitions.
         // In the mean time we do an easy fix here.
-        final boolean show = isVisible() || isAnimating(TRANSITION | PARENTS | CHILDREN);
+        final boolean visible = isVisible();
+        final boolean show = visible || isAnimating(TRANSITION | PARENTS | CHILDREN);
         if (mSurfaceControl != null) {
             if (show != mLastSurfaceShowing) {
                 t.setVisibility(mSurfaceControl, show);
             }
         }
+        // Only show the overlay if the task has other visible children
+        if (mOverlayHost != null) {
+            mOverlayHost.setVisibility(t, visible);
+        }
         mLastSurfaceShowing = show;
     }
 

services/core/java/com/android/server/wm/TrustedOverlayHost.java

@@ -80,6 +80,12 @@ class TrustedOverlayHost {
         }
     }
 
+    void setVisibility(SurfaceControl.Transaction t, boolean visible) {
+        if (mSurfaceControl != null) {
+            t.setVisibility(mSurfaceControl, visible);
+        }
+    }
+
     void addOverlay(SurfaceControlViewHost.SurfacePackage p, SurfaceControl currentParent) {
         requireOverlaySurfaceControl();
         mOverlays.add(p);