Docs:
https://github.com/electron/electron/blob/master/docs/api/session.md#sesclearstoragedataoptions-callback

I was running into a strange error when calling the `clearStorageData` method. It was saying it was unable to process the argument at index 1, which I was not passing. After some research I found that the callback is currently required, but in my case I did not care to provide one. To fix it, I supplied an empty function. Here is my code:

```
Electron.remote.getCurrentWebContents().session.clearStorageData(
    {
        storages: [
            'appcache',
            'cookies',
            'filesystem',
            'indexdb',
            'localstorage',
            'shadercache',
            'websql',
            'serviceworkers',
        ],
        quotas: [
            'temporary',
            'persistent',
            'syncable',
        ],
    },
    function() {} // <--- I shouldn't have to do this
);
```
- Electron version: 1.2.7
- Operating system: macOS

atom/browser/api/atom_api_session.cc
uint32_t storage_mask = 0;
  for (const auto& it : storage_types) {
    auto type = base::ToLowerASCII(it);
    if (type == "appcache")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_APPCACHE;
    else if (type == "cookies")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_COOKIES;
    else if (type == "filesystem")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_FILE_SYSTEMS;
    else if (type == "indexdb")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_INDEXEDDB;
    else if (type == "localstorage")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_LOCAL_STORAGE;
    else if (type == "shadercache")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_SHADER_CACHE;
    else if (type == "websql")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_WEBSQL;
    else if (type == "serviceworkers")
      storage_mask |= StoragePartition::REMOVE_DATA_MASK_SERVICE_WORKERS;
  }
  return storage_mask;
}
uint32_t GetQuotaMask(const std::vector<std::string>& quota_types) {