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

samples/clock/clock.dart

Index: samples/clock/clock.dart
diff --git a/samples/clock/clock.dart b/samples/clock/clock.dart
index c6e6d95f109e6c58a432989b83ed48b77a79079f..b26224ce015b16235712ffda5cfcd28eae4d526b 100644
--- a/samples/clock/clock.dart
+++ b/samples/clock/clock.dart
@@ -5,6 +5,7 @@
 #library("clock");
 
 #import('dart:html');
+#import('dart:math', prefix: "Math");
 
 #source('balls.dart');
 #source('numbers.dart');