Provide list of service protocol extensions in isolate and emit an event when one is registered

runtime/observatory/tests/service/developer_extension_test.dart

 // Copyright (c) 2015, 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.
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:developer';
 import 'package:observatory/service_io.dart';
 import 'package:observatory/cpu_profile.dart';
@@ skipping 37 matching lines @@
 }
 
 Future<ServiceExtensionResponse> LanguageErrorHandler(String method,
                                                       Map paremeters) {
   // The following is an intentional syntax error.
   klajsdlkjfad
 }
 
 void test() {
   registerExtension('__delay', Handler);
+  debugger();
   registerExtension('__error', Handler);
   registerExtension('__exception', Handler);
   registerExtension('__null', Handler);
   registerExtension('__nullFuture', Handler);
   registerExtension('__success', Handler);
   bool exceptionThrown = false;
   try {
     registerExtension('__delay', Handler);
   } catch (e) {
     exceptionThrown = true;
   }
   expect(exceptionThrown, isTrue);
   registerExtension('__languageError', LanguageErrorHandler);
 }
 
 var tests = [
+  hasStoppedAtBreakpoint,
+  (Isolate isolate) async {
+    await isolate.load();
+    expect(isolate.extensionRPCs.length, 1);
+    expect(isolate.extensionRPCs[0], equals('__delay'));
+  },
+  resumeIsolateAndAwaitEvent(VM.kIsolateStream, (ServiceEvent event) {
+    // Check that we received an event when '__error' was registered.
+    expect(event.kind, equals(ServiceEvent.kServiceExtensionAdded));
+    expect(event.extensionRPC, equals('__error'));
+  }),
   // Initial.
   (Isolate isolate) async {
     var result;
 
     result = await isolate.invokeRpcNoUpgrade('__delay', {});
     expect(result['type'], equals('_delayedType'));
     expect(result['method'], equals('__delay'));
     expect(result['parameters']['isolateId'], isNotNull);
 
     try {
@@ skipping 39 matching lines @@
       expect(e.code, equals(ServiceExtensionResponse.kExtensionError));
       expect(e.message, stringContainsInOrder([
           'Error in extension `__languageError`:',
           'developer_extension_test.dart',
           'semicolon expected']));
     }
 
   },
 ];
 
-main(args) async => runIsolateTests(args, tests, testeeBefore:test);
+main(args) async => runIsolateTests(args, tests, testeeConcurrent:test);