Create default implementation for getSyncTarget

AttachedSurfaceControl is a public API so hidden APIs need to be
implemented. Create a default implementation for a new hidden API to
ensure backwards compatibility.

Test: testRuntimeCompatibilityWithCurrentApi_android_net_ipsec_ike
Fixes: 240300753
Change-Id: I4aec403e4bc13e2db902a291f1e42d8fe3d8fdf3

core/java/android/view/AttachedSurfaceControl.java

@@ -145,5 +145,8 @@ public interface AttachedSurfaceControl {
      *
      * @hide
      */
-    SurfaceSyncGroup.SyncTarget getSyncTarget();
+    @Nullable
+    default SurfaceSyncGroup.SyncTarget getSyncTarget() {
+        return null;
+    }
 }

core/java/android/window/SurfaceSyncGroup.java

@@ -186,7 +186,11 @@ public final class SurfaceSyncGroup {
         if (viewRoot == null) {
             return false;
         }
-        return addToSync(viewRoot.getSyncTarget());
+        SyncTarget syncTarget = viewRoot.getSyncTarget();
+        if (syncTarget == null) {
+            return false;
+        }
+        return addToSync(syncTarget);
     }
 
     /**