guard references to SkColorTable

Bug: skia:6828
Change-Id: I0c8c78e70b118f51cb59dc45675e4ddcd4776108
Reviewed-on: https://skia-review.googlesource.com/24260
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
35 files changed