* Electron version: 1.7.4
* Operating system: macOS Sierra

### Expected behavior

Load the PDF file correctly.

### Actual behavior

When I try to load something like http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1118&context=podimproveacad, the '&' symbol seems to interrupt the PDF Viewer to load the file.
![](http://i.imgur.com/RDSeY2u.png)

You can see that part of query string behind '&' get chopped, and I believe this is the reason why the PDF Viewer failed to load.

### How to reproduce

Clone the reproducible project at https://github.com/qazbnm456/electron-quick-start.
```
$ yarn # install packages
$ yarn run start # start the electron
```
atom/browser/atom_resource_dispatcher_host_delegate.cc
const GURL& original_url,
    const content::ResourceRequestInfo::WebContentsGetter&
        web_contents_getter) {
  content::WebContents* web_contents = web_contents_getter.Run();
  if (!web_contents)
    return;
  if (!WebContentsPreferences::IsPluginsEnabled(web_contents)) {
    auto browser_context = web_contents->GetBrowserContext();
    auto download_manager =
      content::BrowserContext::GetDownloadManager(browser_context);
    download_manager->DownloadUrl(
        content::DownloadUrlParameters::CreateForWebContentsMainFrame(
            web_contents, original_url));
    return;
  }
  
  
  
  content::NavigationController::LoadURLParams params(
      GURL(base::StringPrintf("%sindex.html?%s=%s", kPdfViewerUIOrigin,
                              kPdfPluginSrc, original_url.spec().c_str())));
  web_contents->GetController().LoadURLWithParams(params);
}
}  
AtomResourceDispatcherHostDelegate::AtomResourceDispatcherHostDelegate() {
}
bool AtomResourceDispatcherHostDelegate::HandleExternalProtocol(