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
#include "atom/browser/api/atom_api_session.h"
#include <string>
#include <vector>
#include "atom/browser/api/atom_api_cookies.h"
#include "atom/browser/api/atom_api_download_item.h"
#include "atom/browser/api/atom_api_protocol.h"
#include "atom/browser/api/atom_api_web_request.h"
#include "atom/browser/browser.h"
#include "atom/browser/atom_browser_context.h"
#include "atom/browser/atom_browser_main_parts.h"
#include "atom/browser/atom_permission_manager.h"
#include "atom/browser/net/atom_cert_verifier.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/content_converter.h"
#include "atom/common/native_mate_converters/gurl_converter.h"
#include "atom/common/native_mate_converters/file_path_converter.h"
#include "atom/common/native_mate_converters/net_converter.h"
#include "atom/common/native_mate_converters/value_converter.h"
#include "atom/common/node_includes.h"
#include "base/files/file_path.h"
#include "base/guid.h"
#include "components/prefs/pref_service.h"