Implement assignment and copy-construction for SkTHashSet/Map.

This will enable us to use SkTHashMap to store our definition maps.

Change-Id: I6017dfa71e1c5e68a20c97e955bb3d3abf347f0d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/323891
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2 files changed