* Electron version: 1.6.1
* Operating system: macOS 10.12.3, Windows 7 64bit

### Expected behavior

Should emit an error on the request object.

### Actual behavior

<img width="420" alt="image" src="https://cloud.githubusercontent.com/assets/99662/23713890/4e9b8f52-041f-11e7-9dfb-e8408bb58670.png">

An uncatchable error happens.

### How to reproduce
```bash
git clone https://github.com/arantes555/electron-net-encoding-testcase.git
cd electron-net-encoding-testcase
npm install
npm start
```

atom/browser/net/atom_url_request.cc
scoped_refptr<net::HttpResponseHeaders> response_headers) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (delegate_)
    delegate_->OnResponseStarted(response_headers);
}
void AtomURLRequest::InformDelegateResponseData(
    scoped_refptr<net::IOBufferWithSize> data) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  
  
  if (delegate_)
    delegate_->OnResponseData(data);
}
void AtomURLRequest::InformDelegateResponseCompleted() const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (delegate_)
    delegate_->OnResponseCompleted();
}
void AtomURLRequest::InformDelegateErrorOccured(const std::string& error,
                                                bool isRequestError) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (delegate_)
    delegate_->OnError(error, isRequestError);
}
}