Remove ability to disable new analysis driver

pkg/analysis_server/lib/src/server/http_server.dart

Index: pkg/analysis_server/lib/src/server/http_server.dart
diff --git a/pkg/analysis_server/lib/src/server/http_server.dart b/pkg/analysis_server/lib/src/server/http_server.dart
index 94eb15d0393757cb70ce5f3c15e7943eafb05506..6541df51cb2346549cf3ea10a1ebe8b5b66fba8b 100644
--- a/pkg/analysis_server/lib/src/server/http_server.dart
+++ b/pkg/analysis_server/lib/src/server/http_server.dart
@@ -126,12 +126,7 @@ class HttpAnalysisServer {
    */
   Future<Null> _handleGetRequest(HttpRequest request) async {
     if (getHandler == null) {
-      if (socketServer.analysisServer.options.enableNewAnalysisDriver) {
-        getHandler = new DiagnosticsSite(socketServer, _printBuffer);
-      } else {
-        getHandler = new ErrorGetHandler(
-            'Diagnostics only supported for the new analysis driver.');
-      }
+      getHandler = new DiagnosticsSite(socketServer, _printBuffer);
     }
     await getHandler.handleGetRequest(request);
   }