Make the SkPathRef GenIDChangeListener ref counted

Bug: skia:
Change-Id: I2780e3fc76153373b4efca6059ded82f4f749325
Reviewed-on: https://skia-review.googlesource.com/133502
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
8 files changed