Remove HostMessages (#7436)

This API was deprecated. Clients should use PlatformMessages instead.

packages/flutter/lib/services.dart

@@ -14,7 +14,6 @@ export 'src/services/asset_bundle.dart';
 export 'src/services/binding.dart';
 export 'src/services/clipboard.dart';
 export 'src/services/haptic_feedback.dart';
-export 'src/services/host_messages.dart';
 export 'src/services/image_cache.dart';
 export 'src/services/image_decoder.dart';
 export 'src/services/image_provider.dart';

packages/flutter/lib/src/services/host_messages.dart

-// Copyright 2016 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.
-
-import 'dart:async';
-
-import 'platform_messages.dart';
-
-/// Deprecated. Use [PlatformMessages] instead.
-@deprecated
-class HostMessages {
-  /// Send a message to the host application.
-  static Future<String> sendToHost(String channel, [String message = '']) {
-    return PlatformMessages.sendString(channel, message);
-  }
-
-  /// Sends a JSON-encoded message to the host application and JSON-decodes the response.
-  static Future<dynamic> sendJSON(String channel, [dynamic json]) {
-    return PlatformMessages.sendJSON(channel, json);
-  }
-
-  /// Register a callback for receiving messages from the host application.
-  static void addMessageHandler(String channel, Future<String> callback(String message)) {
-    PlatformMessages.setStringMessageHandler(channel, callback);
-  }
-
-  /// Register a callback for receiving JSON messages from the host application.
-  ///
-  /// Messages received from the host application are decoded as JSON before
-  /// being passed to `callback`. The result of the callback is encoded as JSON
-  /// before being returned to the host application.
-  static void addJSONMessageHandler(String channel, Future<dynamic> callback(dynamic json)) {
-    PlatformMessages.setJSONMessageHandler(channel, callback);
-  }
-}