Fix recently introduced strong-mode errors

pkg/analyzer/test/generated/analysis_context_factory.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.
 
 library analyzer.test.generated.analysis_context_factory;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 208 matching lines @@
           null);
       thenOnValue.synthetic = true;
 
       DartType futureRType = futureElement.type.instantiate([futureThenR.type]);
       MethodElementImpl thenMethod = ElementFactory
           .methodElementWithParameters(futureElement, "then", futureRType, [
         ElementFactory.requiredParameter2("onValue", thenOnValue.type),
         ElementFactory.namedParameter2("onError", provider.functionType)
       ]);
       if (!futureThenR.type.isDynamic) {
-        thenMethod.typeParameters = [futureThenR];
+        thenMethod.typeParameters = <TypeParameterElement>[futureThenR];
       }
       thenOnValue.enclosingElement = thenMethod;
       thenOnValue.type = new FunctionTypeImpl(thenOnValue);
       (thenMethod.parameters[0] as ParameterElementImpl).type =
           thenOnValue.type;
       thenMethod.type = new FunctionTypeImpl(thenMethod);
 
       futureElement.methods = <MethodElement>[thenMethod];
       // Completer
       ClassElementImpl completerElement =
@@ skipping 348 matching lines @@
 
   void _addLibrary(LibraryMap map, String uri, bool isInternal, String path) {
     SdkLibraryImpl library = new SdkLibraryImpl(uri);
     if (isInternal) {
       library.category = "Internal";
     }
     library.path = path;
     map.setLibrary(uri, library);
   }
 }