update/add benches to look at colorspace as well as alphatype

Example run:

  24/24  MB	14	332µs	338µs	337µs	341µs	gl	readpix_um_bgra_srgb
  24/24  MB	9	568µs	581µs	581µs	595µs	glsrgb	readpix_um_bgra_srgb
  29/29  MB	10	334µs	340µs	340µs	351µs	gl	readpix_um_bgra_null
  28/29  MB	8	553µs	593µs	592µs	626µs	glsrgb	readpix_um_bgra_null
  32/32  MB	15	334µs	338µs	344µs	388µs	gl	readpix_um_rgba_srgb
  31/32  MB	9	546µs	574µs	571µs	595µs	glsrgb	readpix_um_rgba_srgb
  32/32  MB	10	332µs	340µs	340µs	351µs	gl	readpix_um_rgba_null
  31/32  MB	8	553µs	587µs	589µs	629µs	glsrgb	readpix_um_rgba_null

  54/54  MB	14	364µs	369µs	370µs	383µs	gl	writepix_um_bgra_srgb
  24/54  MB	19	278µs	290µs	288µs	294µs	glsrgb	writepix_um_bgra_srgb
  58/58  MB	14	365µs	376µs	375µs	381µs	gl	writepix_um_bgra_null
  27/58  MB	19	280µs	291µs	291µs	314µs	glsrgb	writepix_um_bgra_null
  59/59  MB	14	368µs	374µs	375µs	382µs	gl	writepix_um_rgba_srgb
  27/59  MB	19	280µs	298µs	295µs	324µs	glsrgb	writepix_um_rgba_srgb
  62/62  MB	14	367µs	378µs	376µs	384µs	gl	writepix_um_rgba_null
  30/62  MB	16	289µs	293µs	296µs	310µs	glsrgb	writepix_um_rgba_null

Bug: skia:
Change-Id: I36e4f68e60a39087c07cf5ff63045a29b56da8f7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/202703
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed