Create a public API for contributing fixes and make fixes pluggable

pkg/analysis_server/test/edit/assists_test.dart

Index: pkg/analysis_server/test/edit/assists_test.dart
diff --git a/pkg/analysis_server/test/edit/assists_test.dart b/pkg/analysis_server/test/edit/assists_test.dart
index 0fcdb80ad27ceed82aeecead42d370c0d3a643d2..fd5f71785cd69b41d12c23b306cfce665bb07506 100644
--- a/pkg/analysis_server/test/edit/assists_test.dart
+++ b/pkg/analysis_server/test/edit/assists_test.dart
@@ -7,7 +7,9 @@ library test.edit.assists;
 import 'dart:async';
 
 import 'package:analysis_server/src/edit/edit_domain.dart';
+import 'package:analysis_server/src/plugin/server_plugin.dart';
 import 'package:analysis_server/src/protocol.dart';
+import 'package:analyzer/src/plugin/plugin_impl.dart';
 import 'package:unittest/unittest.dart' hide ERROR;
 
 import '../analysis_abstract.dart';
@@ -39,7 +41,10 @@ class AssistsTest extends AbstractAnalysisTest {
   void setUp() {
     super.setUp();
     createProject();
-    handler = new EditDomainHandler(server);
+    ExtensionManager manager = new ExtensionManager();
+    ServerPlugin plugin = new ServerPlugin();
+    manager.processPlugins([plugin]);
+    handler = new EditDomainHandler(server, plugin);
   }
 
   Future test_removeTypeAnnotation() {