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
g_wrap_session = callback;
}
}  
}  
namespace {
v8::Local<v8::Value> FromPartition(
    const std::string& partition, mate::Arguments* args) {
  if (!atom::Browser::Get()->is_ready()) {
    args->ThrowError("Session can only be received when app is ready");
    return v8::Null(args->isolate());
  }
  base::DictionaryValue options;
  args->GetNext(&options);
  return atom::api::Session::FromPartition(
      args->isolate(), partition, options).ToV8();
}
void Initialize(v8::Local<v8::Object> exports, v8::Local<v8::Value> unused,
                v8::Local<v8::Context> context, void* priv) {
  v8::Isolate* isolate = context->GetIsolate();
  mate::Dictionary dict(isolate, exports);
  dict.SetMethod("fromPartition", &FromPartition);
  dict.SetMethod("_setWrapSession", &atom::api::SetWrapSession);
}
}  
NODE_MODULE_CONTEXT_AWARE_BUILTIN(atom_browser_session, Initialize)