Fix DefaultGeoProc member variable names

The pattern appears to be that the variable that stores the uploaded
value has a "Prev" suffix.

Change-Id: I78ea449d75f5fd091c113cf08af919331467eb8d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/350638
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed