IMA: Support manual ad break timing

I saw in the following document that I can control the ad break playback timings, but I don't have access to the adsManager in the IMA extension, so I can't control it?
If there is a way to do this, I would like to know about it.
https://developers.google.com/interactive-media-ads/docs/sdks/android/client-side/manual_ad_playback

```java
@Override
public void onAdEvent(AdEvent adEvent) {
...
switch (adEvent.getType()) {
// Listen for the AD_BREAK_READY event.
case AD_BREAK_READY:
// Tell the SDK to play ads when you're ready. To skip this ad break,
// simply return from this handler without calling adsManager.start().
adsManager.start();
break;
...
```