Handle local invoke in inferrer

tests/compiler/dart2js/inference/data/locals.dart

 // Copyright (c) 2017, 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.
 
 /*element: main:[null]*/
 main() {
   uninitializedLocal();
   initializedLocal();
   updatedLocal();
+  invokeLocal();
+  postfixLocal();
 }
 
 /*element: uninitializedLocal:[null]*/
 uninitializedLocal() {
   var local;
   return local;
 }
 
 /*element: initializedLocal:[exact=JSUInt31]*/
 initializedLocal() {
   var local = 0;
   return local;
 }
 
 /*element: updatedLocal:[exact=JSUInt31]*/
 updatedLocal() {
   var local2;
   local2 = 0;
   return local2;
 }
+
+/*element: invokeLocal:[null]*/
+invokeLocal() {
+  var local2 = 0;
+  local2. /*invoke: [exact=JSUInt31]*/ toString();
+  return null;
+}
+
+/*element: postfixLocal:[null]*/
+postfixLocal() {
+  // ignore: UNUSED_LOCAL_VARIABLE
+  var local2 = 0;
+  local2 /*invoke: [exact=JSUInt31]*/ ++;
+  return null;
+}