Prepare for Socket implements Stream<Uint8List> (#35646)

An upcoming change in the Dart SDK changes `Socket` from
implementing `Stream<List<int>>` to implementing `Stream<Uint8List>`.
This forwards-compatible change in flutter_tools prepares for that
Dart SDK change.

https://github.com/dart-lang/sdk/issues/36900
diff --git a/packages/flutter_tools/test/android/android_device_test.dart b/packages/flutter_tools/test/android/android_device_test.dart
index 198b908..f04ea40 100644
--- a/packages/flutter_tools/test/android/android_device_test.dart
+++ b/packages/flutter_tools/test/android/android_device_test.dart
@@ -4,6 +4,7 @@
 
 import 'dart:async';
 import 'dart:convert';
+import 'dart:typed_data';
 
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/android/android_console.dart';
@@ -574,7 +575,7 @@
   final StreamController<String> _controller = StreamController<String>();
 
   @override
-  Stream<E> asyncMap<E>(FutureOr<E> convert(List<int> event)) => _controller.stream as Stream<E>;
+  Stream<E> asyncMap<E>(FutureOr<E> convert(Uint8List event)) => _controller.stream as Stream<E>;
 
   @override
   void add(List<int> data) {
@@ -595,7 +596,7 @@
   final StreamController<String> _controller = StreamController<String>();
 
   @override
-  Stream<E> asyncMap<E>(FutureOr<E> convert(List<int> event)) => _controller.stream as Stream<E>;
+  Stream<E> asyncMap<E>(FutureOr<E> convert(Uint8List event)) => _controller.stream as Stream<E>;
 
   @override
   void add(List<int> data) {}