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* Electron version: 1.6.1
* Operating system: macOS

### Expected behavior

navigator.geolocation.getCurrentPosition runs in background

### Actual behavior

the entire UI is frozen

### How to reproduce

```js
    navigator.geolocation.getCurrentPosition((pos) => {
      console.log('POS: ' + pos);
    }, (err) => {
      console.log('Geolocation error: ', err);
    }, {enableHighAccuracy: false});
```
atom/browser/atom_access_token_store.cc
browser_context_ = AtomBrowserContext::From("", false);
  device::GeolocationProvider::GetInstance()->UserDidOptIntoLocationServices();
}
AtomAccessTokenStore::~AtomAccessTokenStore() {
}
void AtomAccessTokenStore::LoadAccessTokens(
    const LoadAccessTokensCallback& callback) {
  scoped_refptr<internal::TokenLoadingJob> job(
      new internal::TokenLoadingJob(callback));
  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                          base::Bind(&AtomAccessTokenStore::RunTokenLoadingJob,
                                     this, base::RetainedRef(job)));
}
void AtomAccessTokenStore::RunTokenLoadingJob(
    scoped_refptr<internal::TokenLoadingJob> job) {
  job->Run(browser_context_.get());
}
void AtomAccessTokenStore::SaveAccessToken(const GURL& server_url,
                                           const base::string16& access_token) {
}
}