Fix cases of variable shadowing in /src/.

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

Change-Id: Ibebddec324c1b6615c8ec3d118e55d1e59757fbe
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/439398
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
6 files changed