AnalyserNode lacks setFftSize

[raub]

Hello.

Walking through the codes, I've just found that lab::AnalyserNode class lacks an ability to set fftSize value, it has only getter. Also lab::RealtimeAnalyser lacks the same thing.

However it exists in chromium's implementation of the above classes. And it doesn't seem to be too hacky. I think this method is needed, because the spec states that this property is settable.

As a temporary workaround I could resort to re-creating the lab::AnalyserNode instance in my JS (bindings) setter, whenever the fftSize value is changed from JS. But it would really be better if we avoided the hackery and put this feature into the core.

[meshula]

A little bit of factoring of RealtimeAnalyser could do the trick. m_analysisFrame and m_magnitudeBuffer need to be reinitialized, and it looks like everything will work fine.

[meshula]

#113

[meshula]

Merged