* 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
DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
  if (!request_) {
    return;
  }
  DCHECK_EQ(request, request_.get());
  scoped_refptr<net::HttpResponseHeaders> response_headers =
      request->response_headers();
  const auto& status = request_->status();
  if (status.is_success()) {
    
    content::BrowserThread::PostTask(
        content::BrowserThread::UI, FROM_HERE,
        base::Bind(&AtomURLRequest::InformDelegateResponseStarted, this,
                   response_headers));
    ReadResponse();
  } else if (status.status() == net::URLRequestStatus::Status::FAILED) {
    
    DoCancelWithError(net::ErrorToString(status.ToNetError()), true);
  }
  
}
void AtomURLRequest::ReadResponse() {
  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
  int bytes_read = -1;
  if (request_->Read(response_read_buffer_.get(), kBufferSize, &bytes_read)) {
    OnReadCompleted(request_.get(), bytes_read);
  }
}
void AtomURLRequest::OnReadCompleted(net::URLRequest* request, int bytes_read) {