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
base::Closure callback;
  args->GetNext(&callback);
  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
      base::Bind(&ClearHostResolverCacheInIO,
                 make_scoped_refptr(browser_context_->GetRequestContext()),
                 callback));
}
void Session::AllowNTLMCredentialsForDomains(const std::string& domains) {
  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
      base::Bind(&AllowNTLMCredentialsForDomainsInIO,
                 make_scoped_refptr(browser_context_->GetRequestContext()),
                 domains));
}
void Session::SetUserAgent(const std::string& user_agent,
                           mate::Arguments* args) {
  browser_context_->SetUserAgent(user_agent);
  std::string accept_lang = l10n_util::GetApplicationLocale("");
  args->GetNext(&accept_lang);
  auto getter = browser_context_->GetRequestContext();
  getter->GetNetworkTaskRunner()->PostTask(
      FROM_HERE,
      base::Bind(&SetUserAgentInIO, getter, accept_lang, user_agent));
}
std::string Session::GetUserAgent() {