Assign relative layer respecting cache.

Use the helper method rather than directly accessing the SurfaceControl
to ensure we cooperate with the cache.

Bug: 78458365
Test: Manual
Change-Id: I7df240838a54497bc56cd4dc0c89e0d58196bbe3
diff --git a/services/core/java/com/android/server/wm/DisplayContent.java b/services/core/java/com/android/server/wm/DisplayContent.java
index c9ff9e3..c70ec1b 100644
--- a/services/core/java/com/android/server/wm/DisplayContent.java
+++ b/services/core/java/com/android/server/wm/DisplayContent.java
@@ -3877,7 +3877,7 @@
      * with {@link #WindowState#assignLayer}
      */
     void assignRelativeLayerForImeTargetChild(SurfaceControl.Transaction t, WindowContainer child) {
-        t.setRelativeLayer(child.getSurfaceControl(), mImeWindowsContainers.getSurfaceControl(), 1);
+        child.assignRelativeLayer(t, mImeWindowsContainers.getSurfaceControl(), 1);
     }
 
     @Override