Hook for overriding the ContextManager and some code clean-up (with more to follow)

pkg/analysis_server/lib/src/socket_server.dart

Index: pkg/analysis_server/lib/src/socket_server.dart
diff --git a/pkg/analysis_server/lib/src/socket_server.dart b/pkg/analysis_server/lib/src/socket_server.dart
index 36e7836652e433396e148ae7a8010bb4910653e1..1968766f2cd48c95968c0b088d02b7089c803b09 100644
--- a/pkg/analysis_server/lib/src/socket_server.dart
+++ b/pkg/analysis_server/lib/src/socket_server.dart
@@ -6,6 +6,7 @@ library socket.server;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/channel/channel.dart';
+import 'package:analysis_server/src/context_manager.dart';
 import 'package:analysis_server/src/plugin/server_plugin.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/index/index.dart';
@@ -28,6 +29,7 @@ class SocketServer {
   final DirectoryBasedDartSdk defaultSdk;
   final InstrumentationService instrumentationService;
   final ServerPlugin serverPlugin;
+  final ContextManager contextManager;
   final ResolverProvider packageResolverProvider;
 
   /**
@@ -42,7 +44,7 @@ class SocketServer {
   List<Plugin> userDefinedPlugins;
 
   SocketServer(this.analysisServerOptions, this.defaultSdk,
-      this.instrumentationService, this.serverPlugin,
+      this.instrumentationService, this.serverPlugin, this.contextManager,
       this.packageResolverProvider);
 
   /**
@@ -82,6 +84,7 @@ class SocketServer {
         new OptimizingPubPackageMapProvider(resourceProvider, defaultSdk),
         index, serverPlugin, analysisServerOptions, defaultSdk,
         instrumentationService,
+        contextManager: contextManager,
         packageResolverProvider: packageResolverProvider,
         rethrowExceptions: false);
     analysisServer.userDefinedPlugins = userDefinedPlugins;