Check if we are driving or following and only start the timers when we
are the driver of the graph.
Ready events from non-drivers are not really a problem because they are
ignored. They only cause unnecessary wakeups in the graph.
When we add a new listener to an object, it will emit the full state
of the object. For this it temporarily sets the change_mask to all
changes. Restore the previous state after this or else we might not
emit the right change_mask for the next listener.
Consider the case where one there are two listeners on an object.
The object emits a change and the first listener wants to enumerate the
changed params. For this is adds a new listener and then triggers the
enumeration. If we set the change_mask to 0 after adding the listener,
the second listener would get a 0 change_mask and fail to update
its state.
Make info parsing a bit easier to read by assigning the key and
value to temporary variables.
Improve the parsing of channelmap using json parser to make it
support more cases.
Add a unit test for channelmap parsing options.
