Change mojo enums to be scoped enums in the generated C++ bindings.

components/filesystem/file_system_impl.cc

Index: components/filesystem/file_system_impl.cc
diff --git a/components/filesystem/file_system_impl.cc b/components/filesystem/file_system_impl.cc
index 90497764cee7a75c11f7ffda0520850f345b3fa2..88de84c1b59f529045753dadc7d09fd4684be8a1 100644
--- a/components/filesystem/file_system_impl.cc
+++ b/components/filesystem/file_system_impl.cc
@@ -90,9 +90,9 @@ void FileSystemImpl::OpenFileSystem(const mojo::String& file_system,
     DirectoryImpl* dir_impl =
         new DirectoryImpl(std::move(directory), path, std::move(temp_dir));
     app_->RegisterDirectoryToClient(dir_impl, std::move(client));
-    callback.Run(FILE_ERROR_OK);
+    callback.Run(FileError::OK);
   } else {
-    callback.Run(FILE_ERROR_FAILED);
+    callback.Run(FileError::FAILED);
   }
 }