* Electron version: 1.6.2
* Operating system: macOS 10.12.3 (Sierra)

### Expected behavior

Scrollable elements should bounce (rubber band) when reaching the bounds if a window's `webPreferences.scrollBounce = true`

### Actual behavior

Bouncing does not happen

### How to reproduce

```javascript
var win = new BrowserWindow({
    width:800,
    height:600,
    webPreferences:{
        scrollBounce:true
    }
});
```

atom/renderer/renderer_client_base.cc
content::RenderFrame* render_frame,
    blink::WebLocalFrame* frame,
    const blink::WebPluginParams& params,
    blink::WebPlugin** plugin) {
  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
  if (params.mimeType.utf8() == content::kBrowserPluginMimeType ||
      params.mimeType.utf8() == kPdfPluginMimeType ||
      command_line->HasSwitch(switches::kEnablePlugins))
    return false;
  *plugin = nullptr;
  return true;
}
content::BrowserPluginDelegate* RendererClientBase::CreateBrowserPluginDelegate(
    content::RenderFrame* render_frame,
    const std::string& mime_type,
    const GURL& original_url) {
  if (mime_type == content::kBrowserPluginMimeType) {
    return new GuestViewContainer(render_frame);
  } else {
    return nullptr;
  }
}
void RendererClientBase::AddSupportedKeySystems(
    std::vector<std::unique_ptr<::media::KeySystemProperties>>* key_systems) {
  AddChromeKeySystems(key_systems);
}
}