For c++, Generate enum classes instead of enum from mojom.

mojo/public/cpp/bindings/tests/versioning_test_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <map>
 
 #include "mojo/public/c/system/main.h"
 #include "mojo/public/cpp/application/application_connection.h"
 #include "mojo/public/cpp/application/application_delegate.h"
 #include "mojo/public/cpp/application/application_runner.h"
@@ skipping 21 matching lines @@
  public:
   explicit HumanResourceDatabaseImpl(
       InterfaceRequest<HumanResourceDatabase> request)
       : strong_binding_(this, request.Pass()) {
     // Pretend that there is already some data in the system.
     EmployeeInfo* info = new EmployeeInfo();
     employees_[1] = info;
     info->employee = Employee::New();
     info->employee->employee_id = 1;
     info->employee->name = "Homer Simpson";
-    info->employee->department = DEPARTMENT_DEV;
+    info->employee->department = Department::DEV;
     info->employee->birthday = Date::New();
     info->employee->birthday->year = 1955;
     info->employee->birthday->month = 5;
     info->employee->birthday->day = 12;
     info->finger_print.resize(1024);
     for (uint32_t i = 0; i < 1024; ++i)
       info->finger_print[i] = i;
   }
 
   ~HumanResourceDatabaseImpl() override {
@@ skipping 63 matching lines @@
 }  // namespace versioning
 }  // namespace test
 }  // namespace mojo
 
 MojoResult MojoMain(MojoHandle application_request) {
   mojo::ApplicationRunner runner(
       new mojo::test::versioning::HumanResourceSystemServer());
 
   return runner.Run(application_request);
 }