- Electron version: 0.37.2
- Operating system: OS X 10.11.3 

https://github.com/atom/electron/pull/4700 added support for the `visibilitychange` event (thank you @zcbenz!), but that event doesn't make its way into `<webview>`s, which are always "visible" regardless of their host page's `document.visibilityState`.

Tested using the following setup

Host page:

``` coffee
console.log "<webview> host page initial visibilityState =", document.visibilityState

document.addEventListener "visibilitychange", ->
  console.log "<webview> host page visibilitychange event, visibilityState =", document.visibilityState
```

`<webview>`:

``` coffee
console.log "<webview> initial visibilityState =", document.visibilityState

addEventListener "visibilitychange", ->
  console.log "<webview> visibilitychange, visibilityState =", document.visibilityState

setInterval ->
  console.log "<webview> visibilityState =", document.visibilityState
, 3000
```

Host page logs:

```
<webview> host page initial visibilityState = visible
<webview> host page visibilitychange event, visibilityState = hidden
<webview> host page visibilitychange event, visibilityState = visible
```

`<webview>` logs:

```
<webview> initial visibilityState = visible
(24) <webview> visibilityState = visible
```

atom/browser/web_contents_preferences.cc
bool node_integration = true;
  web_preferences.GetBoolean(options::kNodeIntegration, &node_integration);
  command_line->AppendSwitchASCII(switches::kNodeIntegration,
                                  node_integration ? "true" : "false");
  
  base::FilePath::StringType preload;
  if (web_preferences.GetString(options::kPreloadScript, &preload)) {
    if (base::FilePath(preload).IsAbsolute())
      command_line->AppendSwitchNative(switches::kPreloadScript, preload);
    else
      LOG(ERROR) << "preload script must have absolute path.";
  } else if (web_preferences.GetString(options::kPreloadURL, &preload)) {
    
    base::FilePath preload_path;
    if (net::FileURLToFilePath(GURL(preload), &preload_path))
      command_line->AppendSwitchPath(switches::kPreloadScript, preload_path);
    else
      LOG(ERROR) << "preload url must be file:// protocol.";
  }
  
  std::string color;
  if (web_preferences.GetString(options::kBackgroundColor, &color))
    command_line->AppendSwitchASCII(switches::kBackgroundColor, color);
  
  double zoom_factor = 1.0;
  if (web_preferences.GetDouble(options::kZoomFactor, &zoom_factor) &&
      zoom_factor != 1.0)
    command_line->AppendSwitchASCII(switches::kZoomFactor,
                                    base::DoubleToString(zoom_factor));