Updates the corelib to the new default specification for interfaces and new factory syntax

corelib/src/date.dart

Index: corelib/src/date.dart
diff --git a/corelib/src/date.dart b/corelib/src/date.dart
index b04b8b6f6cbce3bf08db5c2e38d315b324768f22..5d16677799638e73a5d5306cc41ca36a45b3e786 100644
--- a/corelib/src/date.dart
+++ b/corelib/src/date.dart
@@ -7,7 +7,7 @@
 /**
  * Date is the public interface to a point in time.
  */
-interface Date extends Comparable factory DateImplementation {
+interface Date extends Comparable default DateImplementation {
   // Weekday constants that are returned by [weekday] method:
   static final int MON = 0;
   static final int TUE = 1;