Fix Issue 8259: dart:math pow broken for large integers.

tests/standalone/pow_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 for testing math's pow.
+
+import 'dart:math';
+
+var expectedResults =
+[
+  1,
+  2,
+  4,
+  8,
+  16,
+  32,
+  64,
+  128,
+  256,
+  512,
+  1024,
+  2048,
+  4096,
+  8192,
+  16384,
+  32768,
+  65536,
+  131072,
+  262144,
+  524288,
+  1048576,
+  2097152,
+  4194304,
+  8388608,
+  16777216,
+  33554432,
+  67108864,
+  134217728,
+  268435456,
+  536870912,
+  1073741824,
+  2147483648,
+  4294967296,
+  8589934592,
+  17179869184,
+  34359738368,
+  68719476736,
+  137438953472,
+  274877906944,
+  549755813888,
+  1099511627776,
+  2199023255552,
+  4398046511104,
+  8796093022208,
+  17592186044416,
+  35184372088832,
+  70368744177664,
+  140737488355328,
+  281474976710656,
+  562949953421312,
+  1125899906842624,
+  2251799813685248,
+  4503599627370496,
+  9007199254740992,
+  18014398509481984,
+  36028797018963968,
+  72057594037927936,
+  144115188075855872,
+  288230376151711744,
+  576460752303423488,
+  1152921504606846976,
+  2305843009213693952,
+  4611686018427387904,
+  9223372036854775808,
+  18446744073709551616,
+  36893488147419103232,
+  73786976294838206464,
+  147573952589676412928
+];
+
+
+void main() {
+  int exp = 0;
+  for (int val in expectedResults) {
+    Expect.equals(val, pow(2, exp++));
+  }
+  // Optimize it.
+  for (int i = 0; i < 8888; i++) {
+    pow(2, 3);
+  }
+  exp = 0;
+  for (int val in expectedResults) {
+    Expect.equals(val, pow(2, exp++));
+  }
+}