public void pauseRequestsRecursive() {
        Util.assertMainThread();
        pauseRequests();
        for (RequestManager requestManager : treeNode.getDescendants()) {
            requestManager.pauseRequests();
        }
    }
Performs {@link #pauseRequests()} recursively for all managers that are contextually descendant
to this manager based on the Activity/Fragment hierarchy:

<ul>
<li>When pausing on an Activity all attached fragments will also get paused.
<li>When pausing on an attached Fragment all descendant fragments will also get paused.
<li>When pausing on a detached Fragment or the application context only the current RequestManager is paused.
</ul>

<p>Note, on pre-Jelly Bean MR1 calling pause on a Fragment will not cause child fragments to pause, in this
case either call pause on the Activity or use a support Fragment.
core/src/main/java/com/bumptech/glide/RequestManager.java