Remove an obsolete error from the spec and an obsolete command-line flag

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 9c28c942f2c18962ba7f4cb02612d7f1c9f8cce1..8e7662ca6087c9cace69647a0cff0cfab2b6a7ce 100644
--- a/pkg/analysis_server/lib/src/socket_server.dart
+++ b/pkg/analysis_server/lib/src/socket_server.dart
@@ -88,16 +88,11 @@ class SocketServer {
           'File read mode was set to the unknown mode: $analysisServerOptions.fileReadMode');
     }
 
-    Index index = null;
-    if (!analysisServerOptions.noIndex) {
-      index = createMemoryIndex();
-    }
-
     analysisServer = new AnalysisServer(
         serverChannel,
         resourceProvider,
         new PubPackageMapProvider(resourceProvider, defaultSdk),
-        index,
+        createMemoryIndex(),
         serverPlugin,
         analysisServerOptions,
         sdkManager,