Bug 770535 - Remove XPConnect test that explicitly runs JS on a seperate thread. v1

This test used to check that we'd error-out properly, but now it'll just cause us to abort.
Bug 770840 - Add Runtime aborts when using XPCWrappedJS off-main-thread. v2
Bug 771074 - Do some more work on nsMainThreadPtrHandle. v2
Bug 771074 - Add opt-out for strict checking in nsMainThreadPtrHolder. v2
Bug 771074 - Fix DNSListenerProxy. v1
Bug 771074 - Fix ServerSocketListenerProxy. v1
Bug 771074 - Make nsRequestObserverProxy proxy events to the main thread only. v1

I'm doing this so that I can safely make this class use nsMainThreadPtr{Handle,Holder}.
There's no theoretical reason why we couldn't support other threads here, but it
would mean implementing that functionality in the PtrHolders, renaming them, and
weakening their assertions/invariants. AFAICT the consumers here don't actually have
a reason to proxy events anywhere but the main thread, so I'm just going to do this
rather than writing code to support something that we don't do (and thus can't test).
Bug 771074 - Make nsRequestObserverProxy hold onto its context. v1

Both the consumers just do this manually. The context here is sometimes an
XPCWrappedJS, so passing it around with nsCOMPtrs off-main-thread can't
happen anymore.

We add assertions in OnStartRequest/OnStopRequest to catch any consumers
that might try to change contexts midstream.
Bug 771074 - Move nsRequestObserverProxy to nsMainThreadPtr{Holder,Handle}. v1
Bug 771074 - Fix wifi listeners. v1
Bug 771074 - Fix Http Activity Distributor. v1
Bug 771074 - Fix nsConsoleService. v1

I had to change mListeners from an nsInterfaceHashtable with nsISupportsHashKey
to an nsRefPtrHashtable with an nsIConsoleListener* hash key. This has two
implications. First, we no longer have to canonicalize key pointers, which is
great because we're only allowing one interface type for keys. Second, we no
longer hold strong refs to our hash key, but this should also be fine because
we hold strong references to our hash value (why isn't this just a hashset
anyway?).
Bug 771074 - Fix KeyGenRunnable. v1
Bug 840592 - Temporarily disable naughty test. v1
remove assertions that can't work with optional strictness.