Make isUtc a getter, change some method names in Date.

runtime/bin/file_impl.dart

Index: runtime/bin/file_impl.dart
diff --git a/runtime/bin/file_impl.dart b/runtime/bin/file_impl.dart
index d53c35be6d5a9996a7e7d6db3417a939126ba5c2..7900aef3586b6e35230033b015436d82b4db1c77 100644
--- a/runtime/bin/file_impl.dart
+++ b/runtime/bin/file_impl.dart
@@ -619,12 +619,13 @@ class _File extends _FileBase implements File {
                                      "Cannot retrieve modification time "
                                      "for file '$_name'");
       }
-      return new Date.fromEpoch(response);
+      return new Date.fromMillisecondsSinceEpoch(response);
     });
   }
 
   Date lastModifiedSync() {
-    return new Date.fromEpoch(_FileUtils.checkedLastModified(_name));
+    int ms = _FileUtils.checkedLastModified(_name);
+    return new Date.fromMillisecondsSinceEpoch(ms);
   }
 
   RandomAccessFile openSync([FileMode mode = FileMode.READ]) {