Clone SourceFactory to ensure that it does not bring a ContentAnalysis reference.

pkg/analyzer/lib/src/dart/analysis/driver.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 159 matching lines @@
    * The controller for the [status] stream.
    */
   final _statusController = new StreamController<AnalysisStatus>();
 
   /**
    * The last status sent to the [status] stream.
    */
   AnalysisStatus _currentStatus = AnalysisStatus.IDLE;
 
   AnalysisDriver(this._logger, this._resourceProvider, this._byteStore,
-      this._contentCache, this._sourceFactory, this._analysisOptions) {
-    _sdkBundle = _sourceFactory.dartSdk.getLinkedBundle();
+      this._contentCache, SourceFactory sourceFactory, this._analysisOptions)
+      : _sourceFactory = sourceFactory.clone() {

[Brian Wilkerson, 2016/10/31 13:16:57]

It seems to me that this ought to be the responsibility of the client, and that
putting this here adds a performance burden that will be paid by all clients
even if they don't need it. Granted that the cost is low, but the principle is
still the same.

+    _sdkBundle = sourceFactory.dartSdk.getLinkedBundle();
   }
 
   /**
    * Set the list of files that the driver should try to analyze sooner.
    *
    * Every path in the list must be absolute and normalized.
    *
    * The driver will produce the results through the [results] stream. The
    * exact order in which results are produced is not defined, neither
    * between priority files, nor between priority and non-priority files.
@@ skipping 1004 matching lines @@
       }
     }
     for (UnlinkedExportPublic export in unit.publicNamespace.exports) {
       referenced.exported.add(export.uri);
     }
     return referenced;
   }
 
   _ReferencedUris._();
 }