Move VariableReference ref-adjusting into helper functions

Change-Id: If2b1e8f89730bfff9e08c1ff5f5cb02c16088d86
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/321117
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
2 files changed