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
const GURL& url) {
    DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
    net::ProxyService* proxy_service =
        context_getter->GetURLRequestContext()->proxy_service();
    net::CompletionCallback completion_callback =
        base::Bind(&ResolveProxyHelper::OnResolveProxyCompleted,
                   base::Unretained(this));
    
    int result = proxy_service->ResolveProxy(
        url, "GET", net::LOAD_NORMAL, &proxy_info_, completion_callback,
        &pac_req_, nullptr, net::BoundNetLog());
    
    if (result != net::ERR_IO_PENDING)
      completion_callback.Run(result);
  }
  Session::ResolveProxyCallback callback_;
  net::ProxyInfo proxy_info_;
  net::ProxyService::PacRequest* pac_req_;
  scoped_refptr<base::SingleThreadTaskRunner> original_thread_;
  DISALLOW_COPY_AND_ASSIGN(ResolveProxyHelper);
};
template<typename ...T>
void RunCallbackInUI(const base::Callback<void(T...)>& callback, T... result) {