Remove the old task model

pkg/analyzer/test/src/mock_sdk.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 test.src.mock_sdk;
 
 import 'package:analyzer/file_system/file_system.dart' as resource;
 import 'package:analyzer/file_system/memory_file_system.dart' as resource;
-import 'package:analyzer/src/context/context.dart' as newContext;
+import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 class MockSdk implements DartSdk {
   static const _MockSdkLibrary LIB_CORE = const _MockSdkLibrary(
       'dart:core',
       '/lib/core/core.dart',
       '''
 library dart.core;
@@ skipping 174 matching lines @@
 
   MockSdk() {
     LIBRARIES.forEach((_MockSdkLibrary library) {
       provider.newFile(library.path, library.content);
     });
   }
 
   @override
   AnalysisContext get context {
     if (_analysisContext == null) {
-      if (AnalysisEngine.instance.useTaskModel) {
-        _analysisContext = new newContext.SdkAnalysisContext();
-      } else {
-        _analysisContext = new SdkAnalysisContext();
-      }
+      _analysisContext = new SdkAnalysisContext();
       SourceFactory factory = new SourceFactory([new DartUriResolver(this)]);
       _analysisContext.sourceFactory = factory;
       ChangeSet changeSet = new ChangeSet();
       for (String uri in uris) {
         Source source = factory.forUri(uri);
         changeSet.addedSource(source);
       }
       _analysisContext.applyChanges(changeSet);
     }
     return _analysisContext;
@@ skipping 104 matching lines @@
   bool get isInternal => throw unimplemented;
 
   @override
   bool get isShared => throw unimplemented;
 
   @override
   bool get isVmLibrary => throw unimplemented;
 
   UnimplementedError get unimplemented => new UnimplementedError();
 }