Online event not firing on iOS or Android

Steps to repeat:
1. Create a Cordova/Ionic app.
2. Listen for onConnect events:
```
document.addEventListener('online', onOnline, false);
function onOnline() {
// This never fires
console.log('I\'m online!');
}
```

```
Cordova:

cordova (Cordova CLI) : 8.1.2 (cordova-lib@8.1.1)
Cordova Platforms : android 7.1.2, ios 4.5.5
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.2, cordova-plugin-ionic-webview 2.1.4, (and 14 other plugins)

System:
Android SDK Tools : 26.1.1 (/Users/username/Library/Android/sdk)
ios-deploy : 1.9.4
ios-sim : 7.0.0
NodeJS : v10.13.0 (/Users/username/.nvm/versions/node/v10.13.0/bin/node)
npm : 6.4.1
OS : macOS High Sierra
Xcode : Xcode 10.1 Build version 10B61
```

Start with the document.addEventListener('online', onOnline, false) entry point and reproduce the report in the listed Cordova/Ionic setup on both iOS and Android. Trace the plugin's platform event handling and verify that the onOnline callback fires on each platform when connectivity changes.

Written by the indexing model from the issue text.