Snap the bitmap as it may be changed later

Bug: skia:
Change-Id: If06510f6fd3b64cce3440a543973c9c83913da10
Reviewed-on: https://skia-review.googlesource.com/120141
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
2 files changed