Make domains plugable

pkg/analysis_server/lib/src/plugin/plugin_impl.dart

Index: pkg/analysis_server/lib/src/plugin/plugin_impl.dart
diff --git a/pkg/analysis_server/lib/src/plugin/plugin_impl.dart b/pkg/analysis_server/lib/src/plugin/plugin_impl.dart
index b4affcf5ee3d6d3f198067abab8f1dc45ebf7183..3c7873b4021a628f4edad82cbfe9b12cdcdd9f86 100644
--- a/pkg/analysis_server/lib/src/plugin/plugin_impl.dart
+++ b/pkg/analysis_server/lib/src/plugin/plugin_impl.dart
@@ -30,9 +30,8 @@ class ExtensionManager {
   void processPlugins(List<Plugin> plugins) {
     for (Plugin plugin in plugins) {
       plugin.registerExtensionPoints(
-          (String identifier, [ExtensionValidator validator]) {
-        registerExtensionPoint(plugin, identifier, validator);
-      });
+          (String identifier, [ExtensionValidator validator]) =>
+              registerExtensionPoint(plugin, identifier, validator));
     }
     for (Plugin plugin in plugins) {
       plugin.registerExtensions(registerExtension);