There are lifetime issues with IconLoader.

Scott notes in https://codereview.chromium.org/2440273002/ :

In reviewing this code it seems like IconManager is racy. In particular
IconManager is not ref counted, but IconLoader is. IconLoader references
IconManager through it's a delegate. This means it's possible for IconLoader to
outlive it's delegate. Seems this function should null out the delegates (and
you should keep the null check in IconLoader::NotifyDelegate).