Cherry-pick r44373, r44378, and r44275.

pkg/analyzer/test/src/task/driver_test.dart

 // Copyright (c) 2015, 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 test.src.task.driver_test;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/cancelable_future.dart';
@@ skipping 496 matching lines @@
   ResolverVisitorFactory get resolverVisitorFactory =>
       baseContext.resolverVisitorFactory;
 
   SourceFactory get sourceFactory => baseContext.sourceFactory;
 
   void set sourceFactory(SourceFactory factory) {
     baseContext.sourceFactory = factory;
   }
 
   @override
+  List<Source> get sources => baseContext.sources;
+
+  @override
   AnalysisContextStatistics get statistics => baseContext.statistics;
 
   @override
   TypeProvider get typeProvider => baseContext.typeProvider;
 
   @override
   TypeResolverVisitorFactory get typeResolverVisitorFactory =>
       baseContext.typeResolverVisitorFactory;
 
   @override
@@ skipping 256 matching lines @@
   void setContents(Source source, String contents) {
     baseContext.setContents(source, contents);
   }
 
   @override
   void visitCacheItems(void callback(Source source, SourceEntry dartEntry,
       DataDescriptor rowDesc, CacheState state)) {
     baseContext.visitCacheItems(callback);
   }
 }