test(VmTurnZone): provide a stub VmTurnZone for CJS tests

modules/angular2/src/core/zone/vm_turn_zone.cjs

@@ -0,0 +1,17 @@
+// TODO(vicb): implement this class properly
+// The current stub implementation is only here to please cjs tests
+export class VmTurnZone {
+  constructor({enableLongStackTrace}) {
+  }
+
+  initCallbacks({onTurnStart, onTurnDone, onScheduleMicrotask, onErrorHandler} = {}) {
+  }
+
+  run(fn) {
+    return fn();
+  }
+
+  runOutsideAngular(fn) {
+    return fn();
+  }
+}