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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/common_web_contents_delegate.cc
auto it = devtools_indexing_jobs_.find(request_id);
  if (it == devtools_indexing_jobs_.end())
    return;
  it->second->Stop();
  devtools_indexing_jobs_.erase(it);
}
void CommonWebContentsDelegate::DevToolsSearchInPath(
    int request_id,
    const std::string& file_system_path,
    const std::string& query) {
  if (!IsDevToolsFileSystemAdded(GetDevToolsWebContents(), file_system_path)) {
    OnDevToolsSearchCompleted(request_id,
                              file_system_path,
                              std::vector<std::string>());
    return;
  }
  devtools_file_system_indexer_->SearchInPath(
      file_system_path,
      query,
      base::Bind(&CommonWebContentsDelegate::OnDevToolsSearchCompleted,
                 base::Unretained(this),
                 request_id,
                 file_system_path));
}
void CommonWebContentsDelegate::OnDevToolsSaveToFile(