Add 'startPaused' option to Isolate.spawn*.

tests/isolate/start_paused_test.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+library start_paused_test;
+
+import "dart:isolate";
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+void isomain(SendPort p) {
+  p.send("DONE");
+}
+
+void notyet(_) {
+  throw "NOT YET";
+}
+
+void main() {
+  asyncStart();
+  test1();
+  test2();
+  asyncEnd();
+}
+
+void test1() {
+  // Test that a paused isolate doesn't send events.
+  // We start two isolates, one paused and one not.
+  // The unpaused one must send an event, after which
+  // we resume that paused isolate, and expect the second event.
+  // This is not a guaranteed test, since it can succeede even if the
+  // paused isolate isn't really paused.
+  // However, it must never fail, since that would mean that a paused
+  // isolate sends a message.
+  asyncStart();
+  RawReceivePort p1 = new RawReceivePort(notyet);
+  Isolate.spawn(isomain, p1.sendPort, paused: true)
+         .then((isolate) {
+    RawReceivePort p2;
+    p2 = new RawReceivePort((x) {
+      Expect.equals("DONE", x);
+      p2.close();
+      p1.handler = (x) {
+        Expect.equals("DONE", x);
+        p1.close();
+        asyncEnd();
+      };
+      isolate.resume(isolate.pauseCapability);
+    });
+    Isolate.spawn(isomain, p2.sendPort);
+  });
+}
+
+void test2() {
+  // Test that a paused isolate doesn't send events.
+  // Like the test above, except that we change the pause capability
+  // of the paused isolate by pausing it using another capability and
+  // then resuming the initial pause. This must not cause it to send
+  // a message before the second pause is resumed as well.
+  asyncStart();
+  RawReceivePort p1 = new RawReceivePort(notyet);
+  Isolate.spawn(isomain, p1.sendPort, paused: true)
+         .then((isolate) {
+    RawReceivePort p2;
+    Capability c2 = new Capability();
+    // Switch to another pause capability.
+    isolate.pause(c2);
+    isolate.resume(isolate.pauseCapability);
+    p2 = new RawReceivePort((x) {
+      Expect.equals("DONE", x);
+      p2.close();
+      p1.handler = (x) {
+        Expect.equals("DONE", x);
+        p1.close();
+        asyncEnd();
+      };
+      isolate.resume(c2);
+    });
+    Isolate.spawn(isomain, p2.sendPort);
+  });
+}