[zetafunction]

The object graph in Chromium is extremely complex. Even if an object's lifetime is managed with a smart pointer, there are often raw pointer back references from other objects. And if some of these objects also have lifetimes coupled to IPC or work happening on other threads… well, you can imagine the result :)

Of course, one could make all the back references weak, but that turns out to also significantly hinder understanding of the code. It ends up being really easy to lose all assertions about when any given object that's weakly reference is actually supposed to be live, and you end up with code that's littered with checks everywhere "just in case".