Migrate language/arithmetic2_test ... language/async_await_syntax_test.

tests/language_2/assertion_initializer_const_function_error_test.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.
 // VMOptions=--assert_initializer
 //
 // Dart test program testing assert statements.
 
 import "package:expect/expect.dart";
 
 class C {
   static bool staticTrue() => true;
   final int x;
   const C(this.x);
   // The expression *is* a compile-time constant, but not a bool value.
   // Static warning, assertion throws which makes it a compile-time error.
   const C.bc02(this.x, y)
       : assert(staticTrue) //# 01: static type warning
       ;
 }
 
 
 main() {
   // Assertion fails, so in checked mode it's a compile-time error.
   // Production mode will succeed because the assertion isn't evaluated.
   var c = const C(1);
   c = const C.bc02(1, 2);  //# 01: compile-time error
   if (c.x != 1) throw "non-trivial use of c";
   Expect.identical(const C(1), c);
 }