add ignore comments for use of deprecated apis

example/grpc-web/lib/app.dart

@@ -14,6 +14,7 @@
 // limitations under the License.
 
 import 'dart:async';
+// ignore: deprecated_member_use (#756)
 import 'dart:html';
 
 import 'src/generated/echo.pbgrpc.dart';

example/grpc-web/web/main.dart

@@ -12,6 +12,8 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+
+// ignore: deprecated_member_use (#756)
 import 'dart:html';
 
 import 'package:grpc/grpc_web.dart';

lib/src/client/transport/xhr_transport.dart

@@ -14,6 +14,7 @@
 // limitations under the License.
 
 import 'dart:async';
+// ignore: deprecated_member_use (#756)
 import 'dart:html';
 import 'dart:typed_data';
 

lib/src/shared/io_bits/io_bits_web.dart

@@ -13,6 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// ignore: deprecated_member_use (#756)
 export 'dart:html' show HttpStatus;
 
 /// Unavailable on the web

test/client_tests/client_xhr_transport_test.dart

@@ -12,10 +12,12 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+
 @TestOn('browser')
 library;
 
 import 'dart:async';
+// ignore: deprecated_member_use (#756)
 import 'dart:html';
 
 import 'package:async/async.dart';