Adjust some tests for limited 64-bit integers

tests/language/bit_shift_test.dart

 // Copyright (c) 2012, 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=--optimization-counter-threshold=10 --no-background-compilation
 
 import "package:expect/expect.dart";
 
+// Note: in --limit-ints-to-64-bits mode all integers are 64-bit already.
+// Still, it is harmless to apply _uint64Mask because (1 << 64) is 0 (all bits
+// are shifted out), so _uint64Mask is -1 (its bit pattern is 0xffffffffffffffff).
+const _uint64Mask = (1 << 64) - 1;
+
 constants() {
   Expect.equals(0, 499 >> 33);
   Expect.equals(0, (499 << 33) & 0xFFFFFFFF);
   Expect.equals(0, (499 << 32) >> 65);
-  Expect.equals(0, ((499 << 32) << 65) & 0xFFFFFFFFFFFFFFFF);
+  Expect.equals(0, ((499 << 32) << 65) & _uint64Mask);
 }
 
 foo(i) {
   if (i != 0) {
     y--;
     foo(i - 1);
     y++;
   }
 }
 
 var y;
 
 // id returns [x] in a way that should be difficult to predict statically.
 id(x) {
   y = x;
   foo(10);
   return y;
 }
 
 interceptors() {
   Expect.equals(0, id(499) >> 33);
   Expect.equals(0, (id(499) << 33) & 0xFFFFFFFF);
   Expect.equals(0, id(499 << 32) >> 65);
-  Expect.equals(0, (id(499 << 32) << 65) & 0xFFFFFFFFFFFFFFFF);
+  Expect.equals(0, (id(499 << 32) << 65) & _uint64Mask);
 }
 
 speculative() {
   var a = id(499);
   var b = id(499 << 32);
   for (int i = 0; i < 1; i++) {
     Expect.equals(0, a >> 33);
     Expect.equals(0, (a << 33) & 0xFFFFFFFF);
     Expect.equals(0, b >> 65);
-    Expect.equals(0, (b << 65) & 0xFFFFFFFFFFFFFFFF);
+    Expect.equals(0, (b << 65) & _uint64Mask);
   }
 }
 
 // JavaScript shifts by the amount modulo 32. That is x << y is equivalent to
 // x << (y & 0x1F). Dart does not.
 main() {
   for (var i = 0; i < 10; ++i) {
     constants();
     interceptors();
     speculative();
   }
 }