Fix cases of variable shadowing in src/.

These were reviewed last year at http://review.skia.org/312480 but never
landed. Splitting into small chunks to land individually.

If we manage to fix all the existing cases of variable shadowing, we
could enable -Wshadow.

Change-Id: I6ae39ce2bdf4cc9fa079e229e21e607088b3cf5d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/435723
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
6 files changed