Make int and double nullable by default

test/checker/inferred_type_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.
 
 /// Tests for type inference.
 library ddc.test.inferred_type_test;
 
 import 'package:unittest/compact_vm_config.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 24 matching lines @@
   });
 
   // Error when declared type is `int` and assigned null.
   testChecker({
     '/main.dart': '''
       test1() {
         int x = 3;
         x = /*warning:DownCastLiteral*/null;
       }
     '''
-  });
+  }, nonnullableTypes: <String>['int', 'double']);
 
   // Error when inferred type is `int` and assigned null.
   testChecker({
     '/main.dart': '''
       test1() {
         var x = 3;
         x = /*warning:DownCastLiteral*/null;
       }
     '''
-  });
+  }, nonnullableTypes: <String>['int', 'double']);
 
   // No error when declared type is `num` and assigned null.
   testChecker({
     '/main.dart': '''
       test1() {
         num x = 3;
         x = null;
       }
     '''
   });
@@ skipping 859 matching lines @@
           I3 get a => null;
         }
 
         class C2 extends A implements B {
           /*severe:InvalidMethodOverride*/get a => null;
         }
     '''
     }, inferFromOverrides: true);
   });
 }