Deprecate Math object in corelib in favor of dart:math library.

utils/tests/string_encoding/utf8_benchmarks.dart

 #!/usr/bin/env 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.
 
 #library("BenchmarkTests");
+#import("dart:math", prefix: "Math");
 #import("../../../lib/utf/utf.dart", prefix: "SE");
 #source("benchmark_runner.dart");
 
 void main() {
 
   final List<int> testEnglishUtf8 = const<int> [
       0x54, 0x68, 0x65, 0x20, 0x71, 0x75, 0x69, 0x63,
       0x6b, 0x20, 0x62, 0x72, 0x6f, 0x77, 0x6e, 0x20,
       0x66, 0x6f, 0x78, 0x20, 0x6a, 0x75, 0x6d, 0x70,
       0x73, 0x20, 0x6f, 0x76, 0x65, 0x72, 0x20, 0x74,
@@ skipping 98 matching lines @@
 
   BenchmarkRunner.runTimed("SE_EL1","string_encoding/decodeUtf8-Greek",
       testConfig_1sec, () =>
           (new SE.Utf8Decoder(testGreekUtf8)).decodeRest());
 
   BenchmarkRunner.runTimed("SE_JA1","string_encoding/decodeUtf8-Katakana",
       testConfig_1sec, () =>
           (new SE.Utf8Decoder(testKatakanaUtf8)).decodeRest());
 }