Index8 is dead, remove guarded code

Needs google3 to be updated before this can land.

Bug: skia:6828
Change-Id: I2c16be13c6937ffa48768cc24f9f980171c824d6
Reviewed-on: https://skia-review.googlesource.com/23940
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Mike Reed <reed@google.com>
30 files changed