Dart: Reorganize files

services/dart/test/interfaces/echo_service.mojom

Index: services/dart/test/interfaces/echo_service.mojom
diff --git a/services/dart/test/interfaces/echo_service.mojom b/services/dart/test/interfaces/echo_service.mojom
deleted file mode 100644
index 1d75fd142421d7c4a4243652773b2a80a312e398..0000000000000000000000000000000000000000
--- a/services/dart/test/interfaces/echo_service.mojom
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-[DartPackage="_mojo_for_test_only"]
-module test;
-
-[ServiceName="test::EchoService"]
-interface EchoService {
-  EchoString(string? value) => (string? value);
-  DelayedEchoString(string? value, int32 millis) => (string? value);
-};