While we typically only call AddHook() for a particular function once, the caller may be initializing lazily. Between the fact that sometimes we can't safely do Nop space patching (see bug 1218473) and the fact that there may be other unintended consequences, we should move as much of this stuff as possible to a safe point during startup. Note that during startup we might not yet have access to the DLL that we want to patch, so we need to be smart about that as well. AddHook loads DLLs if they're not present yet, but during startup we need to be careful about adversely affecting startup time or loading a DLL too early (we need to have the DLL blocklist hooked *before* loading user32.dll, for example).

I've got a WIP that runs as long as I have a patch for bug 1249849 in the queue.