Make ~/, round, ceil, floor, truncate return ints. Remove toInt.

runtime/lib/date_patch.dart

Index: runtime/lib/date_patch.dart
diff --git a/runtime/lib/date_patch.dart b/runtime/lib/date_patch.dart
index 349245e7491c074d49280756c487e29e43b3f1a3..99d30983d356757a6b6b398e7049c0682f3e166f 100644
--- a/runtime/lib/date_patch.dart
+++ b/runtime/lib/date_patch.dart
@@ -183,7 +183,7 @@ patch class _DateImpl {
     // Simplify calculations by working with zero-based month.
     --month;
     // Deal with under and overflow.
-    year += (month / 12).floor().toInt();
+    year += (month / 12).floor();
     month = month % 12;
 
     // First compute the seconds in UTC, independent of the [isUtc] flag. If