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

mojo/services/files/public/c/tests/util_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/c/lib/util.h"
 
 #include "files/public/interfaces/types.mojom.h"
 #include "mojo/public/cpp/system/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojio {
 namespace {
 
 // TODO(vtl): This test is pretty lame until |mojo::files::Error| can also
 // encapsulate "real" errno values.
 TEST(UtilTest, ErrorToErrno) {
   const struct ExpectedMapping {
     mojo::files::Error from;
     int to;
   } kExpectedMappings[] = {
-      {mojo::files::ERROR_OK, 0},
-      {mojo::files::ERROR_UNKNOWN, EIO},
-      {mojo::files::ERROR_INVALID_ARGUMENT, EINVAL},
-      {mojo::files::ERROR_PERMISSION_DENIED, EACCES},
-      {mojo::files::ERROR_OUT_OF_RANGE, EINVAL},
-      {mojo::files::ERROR_UNIMPLEMENTED, ENOSYS},
-      {mojo::files::ERROR_CLOSED, EBADF},
-      {mojo::files::ERROR_UNAVAILABLE, EACCES},
-      {mojo::files::ERROR_INTERNAL, EIO},
+      {mojo::files::Error::OK, 0},
+      {mojo::files::Error::UNKNOWN, EIO},
+      {mojo::files::Error::INVALID_ARGUMENT, EINVAL},
+      {mojo::files::Error::PERMISSION_DENIED, EACCES},
+      {mojo::files::Error::OUT_OF_RANGE, EINVAL},
+      {mojo::files::Error::UNIMPLEMENTED, ENOSYS},
+      {mojo::files::Error::CLOSED, EBADF},
+      {mojo::files::Error::UNAVAILABLE, EACCES},
+      {mojo::files::Error::INTERNAL, EIO},
   };
 
   for (size_t i = 0; i < MOJO_ARRAYSIZE(kExpectedMappings); i++) {
     const ExpectedMapping& m = kExpectedMappings[i];
     EXPECT_EQ(m.to, ErrorToErrno(m.from)) << "i=" << i << ", m.from=" << m.from;
   }
 }
 
 }  // namespace
 }  // namespace mojio