simplify nextRange(), fold in nextEnum()

Doesn't look like we need to distinguish these if we just
write them as the simple

   1) load the right number of bytes
   2) clamp to [min,max]

This makes enum fuzzing independent of its underlying type, and may make
it easier to see the mapping from fuzzed byte stream to
nextRange()/nextEnum() values.

Change-Id: I9f785f94f513a0087ad7151b5e7bc14ddbe9314a
Reviewed-on: https://skia-review.googlesource.com/c/171820
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
5 files changed