[flutter_tools] ensure allowExistingDdsInstance param is always non-null (#74091)

diff --git a/packages/flutter_tools/lib/src/resident_runner.dart b/packages/flutter_tools/lib/src/resident_runner.dart
index 59243f6..5b9bad2 100644
--- a/packages/flutter_tools/lib/src/resident_runner.dart
+++ b/packages/flutter_tools/lib/src/resident_runner.dart
@@ -222,7 +222,7 @@
     int ddsPort,
     bool disableServiceAuthCodes = false,
     bool disableDds = false,
-    bool allowExistingDdsInstance = false,
+    @required bool allowExistingDdsInstance,
     bool ipv6 = false,
   }) {
     final Completer<void> completer = Completer<void>();
@@ -1217,7 +1217,7 @@
     Restart restart,
     CompileExpression compileExpression,
     GetSkSLMethod getSkSLMethod,
-    bool allowExistingDdsInstance,
+    @required bool allowExistingDdsInstance,
   }) async {
     if (!debuggingOptions.debuggingEnabled) {
       throw 'The service protocol is not enabled.';
diff --git a/packages/flutter_tools/lib/src/run_cold.dart b/packages/flutter_tools/lib/src/run_cold.dart
index 8410f8e..75fdc72 100644
--- a/packages/flutter_tools/lib/src/run_cold.dart
+++ b/packages/flutter_tools/lib/src/run_cold.dart
@@ -73,7 +73,9 @@
     if (debuggingOptions.debuggingEnabled) {
       try {
         await Future.wait(<Future<void>>[
-          connectToServiceProtocol(),
+          connectToServiceProtocol(
+            allowExistingDdsInstance: false,
+          ),
           serveDevToolsGracefully(
             devToolsServerAddress: debuggingOptions.devToolsServerAddress,
           ),
diff --git a/packages/flutter_tools/test/general.shard/resident_runner_test.dart b/packages/flutter_tools/test/general.shard/resident_runner_test.dart
index 91d4c58..3166445 100644
--- a/packages/flutter_tools/test/general.shard/resident_runner_test.dart
+++ b/packages/flutter_tools/test/general.shard/resident_runner_test.dart
@@ -197,6 +197,7 @@
       restart: anyNamed('restart'),
       compileExpression: anyNamed('compileExpression'),
       getSkSLMethod: anyNamed('getSkSLMethod'),
+      allowExistingDdsInstance: anyNamed('allowExistingDdsInstance'),
     )).thenAnswer((Invocation invocation) async { });
     when(mockFlutterDevice.setupDevFS(any, any))
       .thenAnswer((Invocation invocation) async {
@@ -2815,7 +2816,7 @@
       observatoryUris: Stream<Uri>.value(testUri),
     );
 
-    await flutterDevice.connect();
+    await flutterDevice.connect(allowExistingDdsInstance: true);
     verify(mockLogReader.connectedVMService = mockVMService);
   }, overrides: <Type, Generator>{
     VMServiceConnector: () => (Uri httpUri, {