Update package:isolate to make kill priority named.

lib/isolate_runner.dart

Index: lib/isolate_runner.dart
diff --git a/lib/isolate_runner.dart b/lib/isolate_runner.dart
index 2d1809513f47737f4b0d3fc6213a3cdf037834d8..fbfe4d61a7e24c3396f6cb0dd43b83a8650410a6 100644
--- a/lib/isolate_runner.dart
+++ b/lib/isolate_runner.dart
@@ -101,13 +101,13 @@ class IsolateRunner implements Runner {
   Future kill({Duration timeout: const Duration(seconds: 1)}) {
     Future onExit = singleResponseFuture(isolate.addOnExitListener);
     if (Duration.ZERO == timeout) {
-      isolate.kill(Isolate.IMMEDIATE);
+      isolate.kill(priority: Isolate.IMMEDIATE);
       return onExit;
     } else {
       // Try a more gentle shutdown sequence.
       _commandPort.send(list1(_SHUTDOWN));
       return onExit.timeout(timeout, onTimeout: () {
-        isolate.kill(Isolate.IMMEDIATE);
+        isolate.kill(priority: Isolate.IMMEDIATE);
         return onExit;
       });
     }