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 "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/thread_task_runner_handle.h"
#include "brightray/browser/net/devtools_network_conditions.h"
#include "brightray/browser/net/devtools_network_controller_handle.h"
#include "chrome/common/pref_names.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/storage_partition.h"
#include "native_mate/dictionary.h"
#include "native_mate/object_template_builder.h"
#include "net/base/load_flags.h"
#include "net/disk_cache/disk_cache.h"
#include "net/dns/host_cache.h"
#include "net/http/http_auth_handler_factory.h"
#include "net/http/http_auth_preferences.h"
#include "net/proxy/proxy_service.h"
#include "net/proxy/proxy_config_service_fixed.h"
#include "net/url_request/static_http_user_agent_settings.h"
#include "net/url_request/url_request_context.h"
#include "net/url_request/url_request_context_getter.h"
#include "ui/base/l10n/l10n_util.h"
using content::BrowserThread;
using content::StoragePartition;
namespace {
struct ClearStorageDataOptions {
  GURL origin;
  uint32_t storage_types = StoragePartition::REMOVE_DATA_MASK_ALL;
  uint32_t quota_types = StoragePartition::QUOTA_MANAGED_STORAGE_MASK_ALL;
};
uint32_t GetStorageMask(const std::vector<std::string>& storage_types) {