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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.h
#ifndef ATOM_BROWSER_ATOM_ACCESS_TOKEN_STORE_H_
#define ATOM_BROWSER_ATOM_ACCESS_TOKEN_STORE_H_
#include "device/geolocation/access_token_store.h"
namespace atom {
class AtomBrowserContext;
namespace internal {
class TokenLoadingJob;
}
class AtomAccessTokenStore : public device::AccessTokenStore {
 public:
  AtomAccessTokenStore();
  ~AtomAccessTokenStore();
  
  void LoadAccessTokens(
      const LoadAccessTokensCallback& callback) override;
  void SaveAccessToken(const GURL& server_url,
                       const base::string16& access_token) override;
 private:
  void RunTokenLoadingJob(scoped_refptr<internal::TokenLoadingJob> job);
  scoped_refptr<AtomBrowserContext> browser_context_;
  DISALLOW_COPY_AND_ASSIGN(AtomAccessTokenStore);
};
}  
#endif