Add documentation to dart:math pow function.

tests/lib/math/math_test.dart

 // Copyright (c) 2011, 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.
 
 library math_test;
 import "package:expect/expect.dart";
 import 'dart:math';
 
 class MathTest {
   static void testConstants() {
@@ skipping 128 matching lines @@
   }
 
   static void testLog() {
     // Even though E is imprecise, it is good enough to get really close to 1.
     // We still provide an epsilon.
     checkClose(1.0, log(E), 1e-16);
     checkVeryClose(LN10, log(10.0));
     checkVeryClose(LN2, log(2.0));
   }
 
-  static void testPow() {
-    checkVeryClose(16.0, pow(4.0, 2.0));
-    checkVeryClose(SQRT2, pow(2.0, 0.5));
-    checkVeryClose(SQRT1_2, pow(0.5, 0.5));
-  }
-
   static bool parseIntThrowsFormatException(str) {
     try {
       int.parse(str);
       return false;
     } on FormatException catch (e) {
       return true;
     }
   }
 
   static void testParseInt() {
@@ skipping 79 matching lines @@
     testSin();
     testCos();
     testTan();
     testAsin();
     testAcos();
     testAtan();
     testAtan2();
     testSqrt();
     testLog();
     testExp();
-    testPow();
     testParseInt();
   }
 }
 
 main() {
   MathTest.testMain();
 }