Mock up all remaining core library implementation classes.

dart/frog/leg/lib/js_helper.dart

Index: dart/frog/leg/lib/js_helper.dart
diff --git a/dart/frog/leg/lib/js_helper.dart b/dart/frog/leg/lib/js_helper.dart
index 714204052bfa979c84ee40e1ba1e3f0224d96a69..d28d6222d981c39d7800b1be3fb8974cdb99c1af 100644
--- a/dart/frog/leg/lib/js_helper.dart
+++ b/dart/frog/leg/lib/js_helper.dart
@@ -338,6 +338,38 @@ class Primitives {
   static num dateNow() => JS("num", @"Date.now()");
 
   static num mathFloor(num value) => JS("num", @"Math.floor($0)", value);
+
+  static brokenDownDateToSecondsSinceEpoch(
+      int years, int month, int day, int hours, int minutes, int seconds,
+      bool isUtc) {
+    throw 'Primitives.brokenDownDateToSecondsSinceEpoch is not implemented';
+  }
+
+  static int getCurrentMs() {
+    throw 'Primitives.getCurrentMs is not implemented';
+  }
+
+  static int getYear(int secondsSinceEpoch, bool isUtc) {
+    throw 'Primitives.getYear is not implemented';
+  }
+
+  static int getMonth(int secondsSinceEpoch, bool isUtc) {
+    throw 'Primitives.getMonth is not implemented';
+  }
+
+  static int getDay_(int secondsSinceEpoch, bool isUtc);
+
+  static int getHours(int secondsSinceEpoch, bool isUtc) {
+    throw 'Primitives.getHours is not implemented';
+  }
+
+  static int getMinutes(int secondsSinceEpoch, bool isUtc) {
+    throw 'Primitives.getMinutes is not implemented';
+  }
+
+  static int getSeconds(int secondsSinceEpoch, bool isUtc) {
+    throw 'Primitives.getSeconds is not implemented';
+  }
 }
 
 builtin$compareTo$1(a, b) {