Wrap chanel result logic in LatchResult

packages/firebase_messaging/android/src/main/java/io/flutter/plugins/firebasemessaging/FlutterFirebaseMessagingService.java

@@ -263,23 +263,7 @@ private static void executeDartCallbackInBackgroundIsolate(
     // If another thread is waiting, then wake that thread when the callback returns a result.
     MethodChannel.Result result = null;
     if (latch != null) {
-      result =
-          new MethodChannel.Result() {
-            @Override
-            public void success(Object result) {
-              latch.countDown();
-            }
-
-            @Override
-            public void error(String errorCode, String errorMessage, Object errorDetails) {
-              latch.countDown();
-            }
-
-            @Override
-            public void notImplemented() {
-              latch.countDown();
-            }
-          };
+      result = new LatchResult(latch).getResult();
     }
 
     Map<String, Object> args = new HashMap<>();

packages/firebase_messaging/android/src/main/java/io/flutter/plugins/firebasemessaging/LatchResult.java

@@ -0,0 +1,35 @@
+package io.flutter.plugins.firebasemessaging;
+
+import java.util.concurrent.CountDownLatch;
+
+import io.flutter.plugin.common.MethodChannel;
+
+public class LatchResult {
+
+  private MethodChannel.Result result;
+
+  public LatchResult(final CountDownLatch latch) {
+    result = new MethodChannel.Result() {
+      @Override
+      public void success(Object result) {
+        latch.countDown();
+      }
+
+      @Override
+      public void error(String errorCode, String errorMessage, Object errorDetails) {
+        latch.countDown();
+      }
+
+      @Override
+      public void notImplemented() {
+        latch.countDown();
+      }
+    };
+  }
+
+  public MethodChannel.Result getResult() {
+    return result;
+  }
+
+
+}