convert isolates to use Future

tests/isolate/src/TestFramework.dart

Index: tests/isolate/src/TestFramework.dart
diff --git a/tests/isolate/src/TestFramework.dart b/tests/isolate/src/TestFramework.dart
index b2a7f286bed4e6073c58aa654667a3fe6fcb1931..97162ba279790417dcf6750567bf4728d8169d2a 100644
--- a/tests/isolate/src/TestFramework.dart
+++ b/tests/isolate/src/TestFramework.dart
@@ -174,7 +174,13 @@ class TestExpectation {
     testCase.tearDown();
   }
 
-  Promise completes(Promise promise) {
+  Promise completes(var promise) {
+    if (!(promise is Promise || promise is Future)) {
+      // TODO(mattsh) - remove this hack once we finish conversion of
+      // Promise to Future
+      throw "must pass Promise or Future to TestFramework.completes";
+    }
+
     Promise result = new TestPromise(this);
     promise.then((value) { result.complete(value); });
     return result;