Fix -Wshadow-field warnings

BUG=skia:

Change-Id: I44f1e11787eab88bdc5ed25c34ea802e9001d427
Reviewed-on: https://skia-review.googlesource.com/9083
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed