Add Driver.useSingleContextManager to turn on single context manager.

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library driver;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:math';
 
@@ skipping 292 matching lines @@
    */
   EmbeddedResolverProvider embeddedUriResolverProvider;
 
   /**
    * The package resolver provider used to override the way package URI's are
    * resolved in some contexts.
    */
   ResolverProvider packageResolverProvider;
 
   /**
+   * If this flag is `true`, then single analysis context should be used for
+   * analysis of multiple analysis roots, special files that could otherwise
+   * cause creating additional contexts, such as `pubspec.yaml`, or `.packages`,
+   * or `.analysis_options` are ignored.
+   */
+  bool useSingleContextManager = false;
+
+  /**
    * The plugins that are defined outside the analysis_server package.
    */
   List<Plugin> _userDefinedPlugins = <Plugin>[];
 
   SocketServer socketServer;
 
   HttpAnalysisServer httpServer;
 
   StdioAnalysisServer stdioServer;
 
@@ skipping 106 matching lines @@
     AnalysisEngine.instance.instrumentationService = service;
     //
     // Create the sockets and start listening for requests.
     //
     socketServer = new SocketServer(
         analysisServerOptions,
         defaultSdkCreator,
         defaultSdk,
         service,
         serverPlugin,
+        embeddedUriResolverProvider,
         packageResolverProvider,
-        embeddedUriResolverProvider);
+        useSingleContextManager);
     httpServer = new HttpAnalysisServer(socketServer);
     stdioServer = new StdioAnalysisServer(socketServer);
     socketServer.userDefinedPlugins = _userDefinedPlugins;
 
     if (serve_http) {
       httpServer.serveHttp(port);
     }
 
     _captureExceptions(service, () {
       stdioServer.serveStdio().then((_) async {
@@ skipping 151 matching lines @@
    */
   static void _rollLogFiles(String path, int numOld) {
     for (int i = numOld - 1; i >= 0; i--) {
       try {
         String oldPath = i == 0 ? path : '$path.$i';
         new File(oldPath).renameSync('$path.${i+1}');
       } catch (e) {}
     }
   }
 }