apply upcoming rule use_collection_literals_when_possible (#8649)

packages/flutter_tools/test/src/mocks.dart

diff --git a/packages/flutter_tools/test/src/mocks.dart b/packages/flutter_tools/test/src/mocks.dart
index 3aac5b5..a8c83df 100644
--- a/packages/flutter_tools/test/src/mocks.dart
+++ b/packages/flutter_tools/test/src/mocks.dart
@@ -77,7 +77,7 @@
 
 /// Common functionality for tracking mock interaction
 class BasicMock {
-  final List<String> messages = new List<String>();
+  final List<String> messages = <String>[];
 
   void expectMessages(List<String> expectedMessages) {
     final List<String> actualMessages = new List<String>.from(messages);