Tabbing away from SMIFF causes playback to happen sporadically

[AJFaraday]

Observed in Chrome on linux, also on windows. May affect other browsers and platforms

• Run up SMIFF
• start playback
• ensure there is some contents in the pattern
• Change to another tab
• Some sounds are hit, seemingly at random, but much less than full playback
• When the browser is on that tab changing window doesn't seem to affect playback

This may be a web audio or JS problem (i.e. setInterval is not running the method all the time or the audio action is not responding). Either way it doesn't appear to be the SMIFF code causing the problem.

I'm stumped, it seems to be outside my control, but I'd welcome any solutions to this problem.

[AJFaraday]

I would be happy with either total playback or explicitly disabling the actions when the window is not focused.

[AJFaraday]

Andrew Duthie (@andrew_duthie) found this article on the reasons for the slow-down for me.

https://codereview.chromium.org/6577021