I showed this chart to clients late last year: it generally got a reaction.
This is data from Baidu showing the share of Android pageviews on its properties that devices from each Android vendor generated. Samsung has about 50% of Android shipments globally - but not in China. 'Other', the swarm of over a thousand small manufacturers making generic devices with (mainly) Mediatek chipsets, is squeezing all the branded OEMs and pushing prices down relentlessly.
(This data is PVs rather than uniques, but one would expect devices from 'other' to be cheaper and have lower PVs per device, implying that the actual share of the base could be even higher.)
Of course, if you look at absolute share of the total base (rather than the Android base) Samsung is still growing fast in China. But the explosion in the 'cheap commodity' sector is not a good sign for any branded Android manufacturer.
Almost none of these devices have any Google services on them, incidentally.