Fix various cases of variable shadowing in Skia.

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

Change-Id: Id8ef6e6962059d0eb2805d68168079f991da1141
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436640
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
7 files changed