Add 'startPaused' option to Isolate.spawn*.

sdk/lib/isolate/isolate.dart

Index: sdk/lib/isolate/isolate.dart
diff --git a/sdk/lib/isolate/isolate.dart b/sdk/lib/isolate/isolate.dart
index 4a5b50a62af7971c82718cc7120e2f0f5e077169..a8063a083e695b133935d081f440d7010259e43f 100644
--- a/sdk/lib/isolate/isolate.dart
+++ b/sdk/lib/isolate/isolate.dart
@@ -58,7 +58,8 @@ class Isolate {
    * Returns a future that will complete with an [Isolate] instance if the
    * spawning succeeded. It will complete with an error otherwise.
    */
-  external static Future<Isolate> spawn(void entryPoint(message), var message);
+  external static Future<Isolate> spawn(void entryPoint(message), var message,
+                                        { bool paused: false });
 
   /**
    * Creates and spawns an isolate that runs the code from the library with
@@ -80,7 +81,7 @@ class Isolate {
    * spawning succeeded. It will complete with an error otherwise.
    */
   external static Future<Isolate> spawnUri(
-      Uri uri, List<String> args, var message);
+      Uri uri, List<String> args, var message, { bool paused: false });
 
 
   /**