Revert two Kernel changes that were causing test failures.

tests/language/assert_assignable_type_test.dart

 // Copyright (c) 2013, 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.
 // Dart test program to test arithmetic operations.
 // VMOptions=--optimization-counter-threshold=10 --checked --no-background-compilation
 
 // This test crashes if we recompute type of AssertAssignableInstr based on its
 // output types. By doing that we would eliminate not only the unnecessary
 // AssertAssignableInstr but also the trailing class check.
 
 main() {
   // Foul up  IC data in integer's unary minus.
   var y = -0x80000000;
   testInt64List();
 }
 
 testInt64List() {
   var array = new List(10);
   testInt64ListImpl(array);
 }
 
 testInt64ListImpl(array) {
   for (int i = 0; i < 10; ++i) {}
   int sum = 0;
   for (int i = 0; i < 10; ++i) {
     array[i] = -0x80000000000000 + i;
   }
 }