[Dart/CLI] : Migrate dart:cli for NNBD.

Change-Id: Ic529d8a69e0073123d68d9b3a190b5cfea4a78ab
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/131487
Reviewed-by: Ben Konyi <bkonyi@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>
Commit-Queue: Siva Annamalai <asiva@google.com>

sdk_nnbd/lib/cli/cli.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.5
-
 /// {@category VM}
 library dart.cli;
 

sdk_nnbd/lib/cli/wait_for.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.5
-
 part of dart.cli;
 
 /**
@@ -55,10 +53,10 @@ void Function(int) _getWaitForEvent() => _waitForEvent;
 // native implementation. In the standalone VM this is set to _waitForEvent()
 // above. If it is null, calling waitFor() will throw an UnsupportedError.
 @pragma("vm:entry-point")
-void Function(int) _waitForEventClosure;
+void Function(int)? _waitForEventClosure;
 
 class _WaitForUtils {
-  static void waitForEvent({Duration timeout}) {
+  static void waitForEvent({Duration? timeout}) {
     if (_waitForEventClosure == null) {
       throw new UnsupportedError("waitFor is not supported by this embedder");
     }
@@ -113,11 +111,11 @@ class _WaitForUtils {
  * subsequent calls block waiting for a condition that is only satisfied when
  * an earlier call returns.
  */
-T waitFor<T>(Future<T> future, {Duration timeout}) {
-  T result;
+T waitFor<T>(Future<T> future, {Duration? timeout}) {
+  late T result;
   bool futureCompleted = false;
-  Object error;
-  StackTrace stacktrace;
+  Object? error;
+  StackTrace? stacktrace;
   future.then((r) {
     futureCompleted = true;
     result = r;
@@ -126,13 +124,13 @@ T waitFor<T>(Future<T> future, {Duration timeout}) {
     stacktrace = st;
   });
 
-  Stopwatch s;
+  late Stopwatch s;
   if (timeout != null) {
     s = new Stopwatch()..start();
   }
   Timer.run(() {}); // Enusre there is at least one message.
   while (!futureCompleted && (error == null)) {
-    Duration remaining;
+    Duration? remaining;
     if (timeout != null) {
       if (s.elapsed >= timeout) {
         throw new TimeoutException("waitFor() timed out", timeout);

sdk_nnbd/lib/libraries.json

@@ -141,9 +141,9 @@
         "uri": "../../sdk/lib/html/dartium/nativewrappers.dart"
       },
       "cli": {
-        "uri": "../../sdk/lib/cli/cli.dart",
+        "uri": "cli/cli.dart",
         "patches": [
-          "../../sdk/lib/_internal/vm/bin/cli_patch.dart"
+          "_internal/vm/bin/cli_patch.dart"
         ]
       },
       "typed_data": {

sdk_nnbd/lib/libraries.yaml

@@ -141,9 +141,9 @@ vm:
       uri: "../../sdk/lib/html/dartium/nativewrappers.dart"
 
     cli:
-      uri: "../../sdk/lib/cli/cli.dart"
+      uri: "cli/cli.dart"
       patches:
-        - "../../sdk/lib/_internal/vm/bin/cli_patch.dart"
+        - "_internal/vm/bin/cli_patch.dart"
 
     typed_data:
       uri: "../../sdk/lib/typed_data/typed_data.dart"