Merge IO v2 branch to bleeding edge

tests/standalone/io/process_kill_test.dart

Index: tests/standalone/io/process_kill_test.dart
diff --git a/tests/standalone/io/process_kill_test.dart b/tests/standalone/io/process_kill_test.dart
index 85719527f986e54699f9e4902a76f8059eb97b6c..733724ff368b7eca35e86c8df848cf63f34b94a0 100644
--- a/tests/standalone/io/process_kill_test.dart
+++ b/tests/standalone/io/process_kill_test.dart
@@ -11,12 +11,12 @@ import "process_test_util.dart";
 testKill() {
   // Start a process that will hang waiting for input until killed.
   Process.start(getProcessTestFileName(), const ["0", "1", "0", "0"]).then((p) {
-    p.onExit = (exitCode) {
+    p.exitCode.then((exitCode) {
       // Process killed from the side so exit code is not 0.
       Expect.isTrue(exitCode != 0);
       // Killing a process that is already dead returns false.
       Expect.isFalse(p.kill());
-    };
+    });
     Expect.isTrue(p.kill());
   });
 }