Prepare for Uint8List SDK breaking changes (#34295)

https://github.com/dart-lang/sdk/issues/36900

dev/devicelab/lib/tasks/save_catalog_screenshots.dart

diff --git a/dev/devicelab/lib/tasks/save_catalog_screenshots.dart b/dev/devicelab/lib/tasks/save_catalog_screenshots.dart
index 389de2d..89ee043 100644
--- a/dev/devicelab/lib/tasks/save_catalog_screenshots.dart
+++ b/dev/devicelab/lib/tasks/save_catalog_screenshots.dart
@@ -65,7 +65,7 @@
       } else {
         // TODO(hansmuller): only retry on 5xx and 429 responses
         logMessage('Request to save "$name" (length ${content.length}) failed with status ${response.statusCode}, will retry');
-        logMessage(await response.transform<String>(utf8.decoder).join());
+        logMessage(await response.cast<List<int>>().transform<String>(utf8.decoder).join());
       }
       return response.statusCode == HttpStatus.ok;
     } on TimeoutException catch (_) {

dev/tools/localization/localizations_utils.dart

diff --git a/dev/tools/localization/localizations_utils.dart b/dev/tools/localization/localizations_utils.dart
index 5f0d8ce..fafe415 100644
--- a/dev/tools/localization/localizations_utils.dart
+++ b/dev/tools/localization/localizations_utils.dart
@@ -299,7 +299,7 @@
   final HttpClient client = HttpClient();
   final HttpClientRequest request = await client.getUrl(Uri.parse(registry));
   final HttpClientResponse response = await request.close();
-  final String body = (await response.transform<String>(utf8.decoder).toList()).join('');
+  final String body = (await response.cast<List<int>>().transform<String>(utf8.decoder).toList()).join('');
   client.close(force: true);
   final List<Map<String, List<String>>> sections = body.split('%%').skip(1).map<Map<String, List<String>>>(_parseSection).toList();
   for (Map<String, List<String>> section in sections) {

packages/flutter_tools/test/base/net_test.dart

diff --git a/packages/flutter_tools/test/base/net_test.dart b/packages/flutter_tools/test/base/net_test.dart
index bbd2678..fc7a29e 100644
--- a/packages/flutter_tools/test/base/net_test.dart
+++ b/packages/flutter_tools/test/base/net_test.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:typed_data';
 
 import 'package:flutter_tools/src/base/io.dart' as io;
 import 'package:flutter_tools/src/base/net.dart';
@@ -216,13 +217,13 @@
   String get reasonPhrase => '<reason phrase>';
 
   @override
-  StreamSubscription<List<int>> listen(
-    void onData(List<int> event), {
+  StreamSubscription<Uint8List> listen(
+    void onData(Uint8List event), {
     Function onError,
     void onDone(),
     bool cancelOnError,
   }) {
-    return Stream<List<int>>.fromFuture(Future<List<int>>.error(const io.SocketException('test')))
+    return Stream<Uint8List>.fromFuture(Future<Uint8List>.error(const io.SocketException('test')))
       .listen(onData, onError: onError, onDone: onDone, cancelOnError: cancelOnError);
   }
 

packages/flutter_tools/test/commands/create_test.dart

diff --git a/packages/flutter_tools/test/commands/create_test.dart b/packages/flutter_tools/test/commands/create_test.dart
index 22fe447..d520b25 100644
--- a/packages/flutter_tools/test/commands/create_test.dart
+++ b/packages/flutter_tools/test/commands/create_test.dart
@@ -4,6 +4,7 @@
 
 import 'dart:async';
 import 'dart:convert';
+import 'dart:typed_data';
 
 import 'package:args/command_runner.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -1303,13 +1304,13 @@
   */
 
   @override
-  StreamSubscription<List<int>> listen(
-    void onData(List<int> event), {
+  StreamSubscription<Uint8List> listen(
+    void onData(Uint8List event), {
     Function onError,
     void onDone(),
     bool cancelOnError,
   }) {
-    return Stream<List<int>>.fromIterable(<List<int>>[result.codeUnits])
+    return Stream<Uint8List>.fromIterable(<Uint8List>[Uint8List.fromList(result.codeUnits)])
       .listen(onData, onError: onError, onDone: onDone, cancelOnError: cancelOnError);
   }