Forwards onConfigurationChanged for PiP on reparenting

This fixes a regression caused by ag/5656236

PiP saves its last position on screen within
AppWindowToken.onConfigurationChanged callback, which is triggered by
Task.reparent before the task leaves pinned stack.

With ag/5656236, Task.reparent no longer triggers
AppWindowToken.onConfigurationChanged and instead, the latter will be
called when the task is added back to its original stack while the
pinned stack no longer exists.

Bug: 142504739
Test: atest PinnedStackTests#testEnterPictureInPictureSavePosition
Change-Id: I247a9da3113077031b442740445d836b0c176986

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

@@ -121,8 +121,11 @@ class Task extends WindowContainer<AppWindowToken> implements ConfigurationConta
     // TODO: Remove after unification.
     @Override
     public void onConfigurationChanged(Configuration newParentConfig) {
-        // Only forward configuration changes in cases where children won't get it from TaskRecord.
-        onConfigurationChanged(newParentConfig, mTaskRecord == null /*forwardToChildren*/);
+        // Forward configuration changes in cases
+        // - children won't get it from TaskRecord
+        // - it's a pinned task
+        onConfigurationChanged(newParentConfig,
+                (mTaskRecord == null) || inPinnedWindowingMode() /*forwardToChildren*/);
     }
 
     Task(int taskId, TaskStack stack, int userId, WindowManagerService service, int resizeMode,