Fix bug in GrResourceAllocator's intermediate flushing (take 2)

Without the missing increment of fCurOpListIndex in the intermediate flush case, the drawing manager could end up re-executing an entire opList.

TBR=bsalomon@google.com
Bug: 942538
Change-Id: I8298c02071e87a343ec03d809959d06049071d93
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/203726
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed