Remove redundant argument-list description code.
Remove redundant argument-list description code.

While reading through this code, I realized we implemented the same
function-argument stringizing loop three times. (A fourth version in
`description()` is similar, but prints the expressions, not types.)

Change-Id: I78610cdf6412b2d08984ac701e6421c356f25a83
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/556076
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Commit-Queue: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia