Restore lazy image cache key logic

This was removed in https://skia-review.googlesource.com/c/skia/+/151661
It appears to be a no-op, but wrapping the original key means that images
and bitmaps with the same unique ID won't hit the same proxies in the
cache.

Change-Id: I9af0594349f22e56af1404c5bcb9e926ded8753e
Reviewed-on: https://skia-review.googlesource.com/153005
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed