add statusChanged event for status synchronization with 3th parties

[pablodgonzalez]

No description provided.

[pablodgonzalez]

@chieffancypants You could check this pull request?
I use this event for synchronizing the loading bar with other visuals elements. But is the bar which controlling load percentage
Cheers!

[faceleg]

How frequently does this event get called? My only concern is that this could cause performance issues.

If this is the case, then it should be off by default and turned on via a config flag.

Also, PR's should be accompanied by appropriate unit tests.

@chieffancypants thoughts?

[chieffancypants]

Is there still a huge performance difference between $broadcast and $emit? If so, this should be changed to $emit, and just force people to listen on $rootScope, which I believe is way more common now anyway.

[faceleg]

Agree that listening on $rootScope is fine for this (therefore $emit)

I'll take @chieffancypants' silence on the config flag and off by default to mean he agrees. And tests :)