First experimental steps towards a better story for JS interop.

lib/isolate/isolate_api.dart

Index: lib/isolate/isolate_api.dart
diff --git a/lib/isolate/isolate_api.dart b/lib/isolate/isolate_api.dart
index 869bf822847ad1ce0305a36aad71f0898600aa1c..3978b939d58145e61e2cc776a7ac32a1cb07777b 100644
--- a/lib/isolate/isolate_api.dart
+++ b/lib/isolate/isolate_api.dart
@@ -90,7 +90,7 @@ interface SendPort extends Hashable {
    * Tests whether [other] is a [SendPort] pointing to the same
    * [ReceivePort] as this one.
    */
-   bool operator==(var other);
+  bool operator==(var other);
 
   /**
    * Returns an immutable hash code for this send port that is
@@ -140,6 +140,13 @@ interface ReceivePort default _ReceivePortFactory {
 
 }
 
+// TODO(kasperl): Make this hashable and document it.
+interface SendPortSync {
+
+  callSync(var message);
+
+}
+
 /**
  * NOTE: This API will be deprecated soon.
  *