Cleanup implicit 64-bit to 32-bit conversions batch 1

Change-Id: I10064972af4e4b8e96131413ed4aee60a58eea29
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/593836
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Herb Derby <herb@google.com>
6 files changed