Cleanup mNativeChildren on react node cleanup.

Differential Revision: D2663443

fb-gh-sync-id: 7e6e7212103b738f6b6f535e54cc8b86e5def685

ReactAndroid/src/main/java/com/facebook/react/uimanager/NativeViewHierarchyOptimizer.java

@@ -90,6 +90,13 @@ public class NativeViewHierarchyOptimizer {
     }
   }
 
+  /**
+   * Handles native children cleanup when css node is removed from hierarchy
+   */
+  public static void handleRemoveNode(ReactShadowNode node) {
+    node.removeAllNativeChildren();
+  }
+
   /**
    * Handles an updateView call. If a view transitions from being layout-only to not (or vice-versa)
    * this could result in some number of additional createView and manageChildren calls. If the