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

mojo/services/files/public/cpp/tests/output_stream_file_unittest.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 "files/public/cpp/output_stream_file.h"
 
 #include <string.h>
 
 #include <memory>
 #include <string>
@@ skipping 61 matching lines @@
   std::string data_;
   bool got_on_closed_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(TestClient);
 };
 
 void TestWrite(mojo::files::File* file,
                TestClient* client,
                const std::string& s) {
   bool write_cb_called = false;
-  mojo::files::Error error = mojo::files::ERROR_INTERNAL;
+  mojo::files::Error error = mojo::files::Error::INTERNAL;
   uint32_t num_bytes_written = 0;
-  file->Write(StringToArray(s), 0, mojo::files::WHENCE_FROM_CURRENT,
+  file->Write(StringToArray(s), 0, mojo::files::Whence::FROM_CURRENT,
               [&write_cb_called, &error, &num_bytes_written](
                   mojo::files::Error e, uint32_t n) {
                 write_cb_called = true;
                 error = e;
                 num_bytes_written = n;
                 QuitMessageLoop();
               });
   if (client) {
     // If there's a client, since we're running everything on one thread, the
     // impl (which will call the client, which will quit the message loop) will
     // get called before the callback.
     client->Reset();
     RunMessageLoop();
     EXPECT_TRUE(client->got_on_data_received());
     EXPECT_EQ(s, client->data());
     EXPECT_FALSE(client->got_on_closed());
     EXPECT_FALSE(write_cb_called);
     // Spin the message loop again to get the callback.
     client->Reset();
     RunMessageLoop();
     EXPECT_FALSE(client->got_on_data_received());
     EXPECT_FALSE(client->got_on_closed());
   } else {
     // Otherwise, only the write callback will be called and quit the message
     // loop.
     RunMessageLoop();
   }
   EXPECT_TRUE(write_cb_called);
-  EXPECT_EQ(mojo::files::ERROR_OK, error);
+  EXPECT_EQ(mojo::files::Error::OK, error);
   EXPECT_EQ(s.size(), num_bytes_written);
 }
 
 void TestClose(mojo::files::File* file, TestClient* client) {
   bool close_cb_called = false;
-  mojo::files::Error error = mojo::files::ERROR_INTERNAL;
+  mojo::files::Error error = mojo::files::Error::INTERNAL;
   file->Close([&close_cb_called, &error](mojo::files::Error e) {
     close_cb_called = true;
     error = e;
     QuitMessageLoop();
   });
   // (This is analogous to |TestWrite()|.)
   if (client) {
     client->Reset();
     RunMessageLoop();
     EXPECT_FALSE(client->got_on_data_received());
     EXPECT_TRUE(client->got_on_closed());
     EXPECT_FALSE(close_cb_called);
     client->Reset();
     RunMessageLoop();
     EXPECT_FALSE(client->got_on_data_received());
     EXPECT_FALSE(client->got_on_closed());
   } else {
     RunMessageLoop();
   }
   EXPECT_TRUE(close_cb_called);
-  EXPECT_EQ(mojo::files::ERROR_OK, error);
+  EXPECT_EQ(mojo::files::Error::OK, error);
 }
 
 TEST_F(OutputStreamFileTest, Basic) {
   mojo::files::FilePtr file;
   TestClient client;
   std::unique_ptr<OutputStreamFile> file_impl =
       OutputStreamFile::Create(&client, GetProxy(&file));
 
   TestWrite(file.get(), &client, "hello");
   TestWrite(file.get(), &client, "world");
@@ skipping 127 matching lines @@
     });
     TestClose(file.get(), nullptr);
     if (!got_connection_error)
       RunMessageLoop();
     EXPECT_TRUE(got_connection_error);
   }
 }
 
 }  // namespace
 }  // namespace files_impl