Extract constants into separate libarary.

pkg/analysis_server/test/socket_server_test.dart

Index: pkg/analysis_server/test/socket_server_test.dart
diff --git a/pkg/analysis_server/test/socket_server_test.dart b/pkg/analysis_server/test/socket_server_test.dart
index fbc15121819062314fed0abdca9aa8668983d288..0f9c083914cb56d228f0122a4f32f4164d2f9327 100644
--- a/pkg/analysis_server/test/socket_server_test.dart
+++ b/pkg/analysis_server/test/socket_server_test.dart
@@ -8,8 +8,7 @@ import 'dart:async';
 
 import 'mocks.dart';
 
-import 'package:analysis_server/src/analysis_server.dart';
-import 'package:analysis_server/src/domain_server.dart';
+import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/socket_server.dart';
 import 'package:unittest/unittest.dart';
@@ -29,11 +28,11 @@ class SocketServerTest {
     MockServerChannel channel = new MockServerChannel();
     server.createAnalysisServer(channel);
     channel.expectMsgCount(notificationCount: 1);
-    expect(channel.notificationsReceived[0].event, equals(
-        AnalysisServer.CONNECTED_NOTIFICATION));
+    expect(channel.notificationsReceived[0].event, NOTIFICATION_CONNECTED);
     expect(channel.notificationsReceived[0].params, isEmpty);
-    return channel.sendRequest(new Request('0',
-        ServerDomainHandler.SHUTDOWN_METHOD)).then((Response response) {
+    return channel.sendRequest(
+        new Request('0', METHOD_SHUTDOWN)
+    ).then((Response response) {
       expect(response.id, equals('0'));
       expect(response.error, isNull);
       channel.expectMsgCount(responseCount: 1, notificationCount: 1);
@@ -45,8 +44,7 @@ class SocketServerTest {
     MockServerChannel channel1 = new MockServerChannel();
     MockServerChannel channel2 = new MockServerChannel();
     server.createAnalysisServer(channel1);
-    expect(channel1.notificationsReceived[0].event, equals(
-        AnalysisServer.CONNECTED_NOTIFICATION));
+    expect(channel1.notificationsReceived[0].event, NOTIFICATION_CONNECTED);
     expect(channel1.notificationsReceived[0].params, isEmpty);
     server.createAnalysisServer(channel2);
     channel1.expectMsgCount(notificationCount: 1);
@@ -55,8 +53,7 @@ class SocketServerTest {
     expect(channel2.responsesReceived[0].error, isNotNull);
     expect(channel2.responsesReceived[0].error.code, equals(
         RequestError.CODE_SERVER_ALREADY_STARTED));
-    channel2.sendRequest(new Request('0', ServerDomainHandler.SHUTDOWN_METHOD)
-        ).then((Response response) {
+    channel2.sendRequest(new Request('0', METHOD_SHUTDOWN)).then((Response response) {
       expect(response.id, equals('0'));
       expect(response.error, isNotNull);
       expect(response.error.code, equals(