- Electron version:
  1.3.3
- Operating system:
  OSX El Capitan

``` javascript
      function cbError(e) {
         console.error('failure', e);
      }

      navigator.webkitPersistentStorage.requestQuota( 10 * 1024* 1024, function(granted) {
        webkitRequestFileSystem(PERSISTENT, granted, cb, cbError);
      },
      cbError)
```

webkitRequestFileSystem is failing with:

```
FileError {code: 2, name: "SecurityError", message: "It was determined that certain files are unsafe fo… too many calls are being made on file resources."}code: 2message: "It was determined that certain files are unsafe for access within a Web application, or that too many calls are being made on file resources."name: "SecurityError"__proto__: FileError
```

This page is being served from a custom:// scheme if that matters.

atom/browser/atom_browser_client.cc
return new AtomAccessTokenStore;
}
void AtomBrowserClient::OverrideWebkitPrefs(
    content::RenderViewHost* host, content::WebPreferences* prefs) {
  prefs->javascript_enabled = true;
  prefs->web_security_enabled = true;
  prefs->javascript_can_open_windows_automatically = true;
  prefs->plugins_enabled = true;
  prefs->dom_paste_enabled = true;
  prefs->allow_scripts_to_close_windows = true;
  prefs->javascript_can_access_clipboard = true;
  prefs->local_storage_enabled = true;
  prefs->databases_enabled = true;
  prefs->application_cache_enabled = true;
  prefs->allow_universal_access_from_file_urls = true;
  prefs->allow_file_access_from_file_urls = true;
  prefs->experimental_webgl_enabled = true;
  prefs->allow_displaying_insecure_content = false;
  prefs->allow_running_insecure_content = false;
  
  auto web_contents = content::WebContents::FromRenderViewHost(host);
  WebContentsPreferences::OverrideWebkitPrefs(web_contents, prefs);
}
std::string AtomBrowserClient::GetApplicationLocale() {
  return l10n_util::GetApplicationLocale("");
}
void AtomBrowserClient::OverrideSiteInstanceForNavigation(