Revert modPow introduction since dart2js does not like it.

sdk/lib/core/int.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.
 
 part of dart.core;
 
 /**
  * An arbitrarily large integer.
  *
  * **Note:** When compiling to JavaScript, integers are
@@ skipping 85 matching lines @@
    * Shift the bits of this integer to the right by [shiftAmount].
    *
    * Shifting to the right makes the number smaller and drops the least
    * significant bits, effectively doing an integer division by
    *`pow(2, shiftIndex)`.
    *
    * It is an error of [shiftAmount] is negative.
    */
   int operator >>(int shiftAmount);
 
-  /** Returns this integer to the power of [exponent] modulo [modulus]. */
-  int modPow(int exponent, int modulus);
-
   /** Returns true if and only if this integer is even. */
   bool get isEven;
 
   /** Returns true if and only if this integer is odd. */
   bool get isOdd;
 
   /**
    * Returns the minimum number of bits required to store this integer.
    *
    * The number of bits excludes the sign bit, which gives the natural length
@@ skipping 153 matching lines @@
    * value is used instead. If no [onError] is provided, a [FormatException]
    * is thrown.
    *
    * The [onError] function is only invoked if [source] is a [String]. It is
    * not invoked if the [source] is, for example, `null`.
    */
   external static int parse(String source,
                             { int radix,
                               int onError(String source) });
 }