Revert two Kernel changes that were causing test failures.

tests/language/assertion_initializer_const_error_test.dart

 // Copyright (c) 201, 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
 
 class C {
   static bool check(x, y) => x < y;
   final int x;
   const C(this.x);
   // The expression is not a potentially constant expression.
   // This is a compile-time error even in production mode.
   const C.bc03(this.x, y)
       : assert(check(x, y))  //# 01: compile-time error
       ;
 }
 
 main() {
   var c = new C.bc03(1, 2);
   if (c.x != 1) throw "non-trivial use of c";
 }