Factor out opcode identification logic.
Factor out opcode identification logic.

This will allow `is_globally_reachable_op` to be used in other places.

Change-Id: I99ea05b0a1da685a24d96700b395b4d13df0993e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/529122
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Commit-Queue: 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