* 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
const std::string& value) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  content::BrowserThread::PostTask(
      content::BrowserThread::IO, FROM_HERE,
      base::Bind(&AtomURLRequest::DoSetExtraHeader, this, name, value));
}
void AtomURLRequest::RemoveExtraHeader(const std::string& name) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  content::BrowserThread::PostTask(
      content::BrowserThread::IO, FROM_HERE,
      base::Bind(&AtomURLRequest::DoRemoveExtraHeader, this, name));
}
void AtomURLRequest::PassLoginInformation(
    const base::string16& username,
    const base::string16& password) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (username.empty() || password.empty()) {
    content::BrowserThread::PostTask(
        content::BrowserThread::IO, FROM_HERE,
        base::Bind(&AtomURLRequest::DoCancelAuth, this));
  } else {
    content::BrowserThread::PostTask(
        content::BrowserThread::IO, FROM_HERE,
        base::Bind(&AtomURLRequest::DoSetAuth, this, username, password));
  }
}
void AtomURLRequest::SetLoadFlags(int flags) const {