Fix method call type inference with explicit type parameters.

pkg/front_end/lib/src/fasta/kernel/body_builder.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 fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
@@ skipping 568 matching lines @@
     push(new ParenthesizedExpression(this, popForValue(), token.endGroup));
   }
 
   @override
   void endSend(Token beginToken, Token endToken) {
     debugEvent("Send");
     Arguments arguments = pop();
     List<DartType> typeArguments = pop();
     Object receiver = pop();
     if (arguments != null && typeArguments != null) {
-      arguments.types.addAll(typeArguments);
+      assert(arguments.types.isEmpty);
+      astFactory.setExplicitArgumentTypes(arguments, typeArguments);
     } else {
       assert(typeArguments == null);
     }
     if (receiver is Identifier) {
       Name name = new Name(receiver.name, library.library);
       if (arguments == null) {
         push(new IncompletePropertyAccessor(this, beginToken, name));
       } else {
         push(new SendAccessor(this, beginToken, name, arguments));
       }
@@ skipping 2530 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is FastaAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }