Cleanup the isolate library to pave the way for web worker support.

tests/compiler/dart2js_extra/isolate2_negative_test.dart

Index: tests/compiler/dart2js_extra/isolate2_negative_test.dart
===================================================================
--- tests/compiler/dart2js_extra/isolate2_negative_test.dart	(revision 16793)
+++ tests/compiler/dart2js_extra/isolate2_negative_test.dart	(working copy)
@@ -4,6 +4,8 @@
 
 // Dart test program for testing that exceptions in other isolates bring down
 // the program.
+// TODO(7769): Remove this test when
+// tests/isolate/isolate2_negative_test passes.
 
 library isolate2_negative_test;
 import 'dart:isolate';
@@ -14,4 +16,5 @@
 
 main() {
   SendPort port = spawnFunction(entry);
+  port.receive((msg) {});
 }